Block #6,784,931

2CCLength 11★★★☆☆

Cunningham Chain of the Second Kind · Discovered 4/5/2026, 10:56:46 PM · Difficulty 10.9809 · 223 confirmations

2CC

Cunningham Chain of the Second Kind

A sequence where each prime is double the previous prime minus one.

Block Header

Block Hash

26d3991c9b0363e4d90d8404ac9ee92cdfe8c7d488150b417713371fd9474d90

View on Chainz ↗

Height

#6,784,931

Difficulty

10.980856

Transactions

Size

199 B

Version

536870912

Bits

0afb1967

Nonce

570,435,972

Timestamp

4/5/2026, 10:56:46 PM

Confirmations

223

Merkle Root

feffa4f662cbc14a3adc35270049d26e54224ffbbf010df0e91b01c14ff97d28

Transactions (1)

Coinbasefeffa4f662cbc1…1b01c14ff97d28

1 in → 1 out8.1710 XPM109 B

AMksgyoK…KsbpjseX

Prime Chain Origin

This is the prime chain origin stored in the block header. It is a composite number (not prime itself) — it equals the first prime in the chain multiplied by a primorial. The origin anchors the entire chain to this specific block.

8.524 × 10⁹⁴(95-digit number)

85249135790788742215…95691583404960061121

Discovered Prime Numbers

p_k = 2^k × origin + 1

These are the actual prime numbers discovered by this block, computed using the verified Primecoin formula. Each number has been independently confirmed to pass the Fermat primality test. Use the FactorDB links to verify any number independently.

origin + 1

8.524 × 10⁹⁴(95-digit number)

85249135790788742215…95691583404960061121

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^1 × origin + 1

1.704 × 10⁹⁵(96-digit number)

17049827158157748443…91383166809920122241

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^2 × origin + 1

3.409 × 10⁹⁵(96-digit number)

34099654316315496886…82766333619840244481

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^3 × origin + 1

6.819 × 10⁹⁵(96-digit number)

68199308632630993772…65532667239680488961

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^4 × origin + 1

1.363 × 10⁹⁶(97-digit number)

13639861726526198754…31065334479360977921

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^5 × origin + 1

2.727 × 10⁹⁶(97-digit number)

27279723453052397508…62130668958721955841

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^6 × origin + 1

5.455 × 10⁹⁶(97-digit number)

54559446906104795017…24261337917443911681

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^7 × origin + 1

1.091 × 10⁹⁷(98-digit number)

10911889381220959003…48522675834887823361

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^8 × origin + 1

2.182 × 10⁹⁷(98-digit number)

21823778762441918007…97045351669775646721

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^9 × origin + 1

4.364 × 10⁹⁷(98-digit number)

43647557524883836014…94090703339551293441

Verify on FactorDB ↗Wolfram Alpha ↗

×2−1 →

2^10 × origin + 1

8.729 × 10⁹⁷(98-digit number)

87295115049767672028…88181406679102586881

Verify on FactorDB ↗Wolfram Alpha ↗

What this block proved

The miner who found this block proved the existence of 11 consecutive prime numbers forming a Cunningham Chain of the Second Kind. The prime chain origin — the large number shown above — anchors the chain and is divisible by a primorial (the product of small primes), cryptographically tying these prime numbers to this specific block.

★★★☆☆

Rarity

RareChain length 11

Approximately 1 in 1,000 blocks. Noteworthy discoveries.

How Primecoin's Proof-of-Work Constructs These Primes

Primecoin stores a value called the prime chain origin in each block. The miner found a large integer such that when divided by a primorial (the product of small primes: 2 × 3 × 5 × 7 × …), the result is the first prime in the chain. The origin is deliberately divisible by this primorial — that divisibility is part of the proof.

Prime Chain Origin = First Prime × Primorial (2·3·5·7·11·…)

Source: Primecoin prime.cpp — CheckPrimeProofOfWork()

This is why the origin has many small prime factors — those factors are the primorial divisor. The chain then extends from the first prime using the 2CC formula:

2CC: p₁ (first prime), p₂ = 2p₁ − 1, p₃ = 2p₂ − 1, …

Cross-reference on Chainz Explorer