Block #1,695,985

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.

1.338 × 10⁹⁷(98-digit number)

13381319326504155667…81051107797755013119

Discovered Prime Numbers

Lower: 2^k × origin − 1 | Upper: 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.

Level 0 — Twin Prime Pair (origin ± 1)

origin − 1

1.338 × 10⁹⁷(98-digit number)

13381319326504155667…81051107797755013119

Verify on FactorDB ↗Wolfram Alpha ↗

origin + 1

1.338 × 10⁹⁷(98-digit number)

13381319326504155667…81051107797755013121

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: origin + 1 − origin − 1 = 2 (twin primes ✓)

Level 1 — Twin Prime Pair (2^1 × origin ± 1)

2^1 × origin − 1

2.676 × 10⁹⁷(98-digit number)

26762638653008311334…62102215595510026239

Verify on FactorDB ↗Wolfram Alpha ↗

2^1 × origin + 1

2.676 × 10⁹⁷(98-digit number)

26762638653008311334…62102215595510026241

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: 2^1 × origin + 1 − 2^1 × origin − 1 = 2 (twin primes ✓)

Level 2 — Twin Prime Pair (2^2 × origin ± 1)

2^2 × origin − 1

5.352 × 10⁹⁷(98-digit number)

53525277306016622668…24204431191020052479

Verify on FactorDB ↗Wolfram Alpha ↗

2^2 × origin + 1

5.352 × 10⁹⁷(98-digit number)

53525277306016622668…24204431191020052481

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: 2^2 × origin + 1 − 2^2 × origin − 1 = 2 (twin primes ✓)

Level 3 — Twin Prime Pair (2^3 × origin ± 1)

2^3 × origin − 1

1.070 × 10⁹⁸(99-digit number)

10705055461203324533…48408862382040104959

Verify on FactorDB ↗Wolfram Alpha ↗

2^3 × origin + 1

1.070 × 10⁹⁸(99-digit number)

10705055461203324533…48408862382040104961

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: 2^3 × origin + 1 − 2^3 × origin − 1 = 2 (twin primes ✓)

Level 4 — Twin Prime Pair (2^4 × origin ± 1)

2^4 × origin − 1

2.141 × 10⁹⁸(99-digit number)

21410110922406649067…96817724764080209919

Verify on FactorDB ↗Wolfram Alpha ↗

2^4 × origin + 1

2.141 × 10⁹⁸(99-digit number)

21410110922406649067…96817724764080209921

Verify on FactorDB ↗Wolfram Alpha ↗

Difference: 2^4 × origin + 1 − 2^4 × origin − 1 = 2 (twin primes ✓)

What this block proved

The miner who found this block proved the existence of 10 consecutive prime numbers forming a Bi-Twin Chain. 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

UncommonChain length 10

Roughly 1 in 100 blocks. Solid but expected in a healthy network.

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 TWN formula:

TWN: twin pairs (p, p+2) where p = origin/primorial − 1 and p+2 = origin/primorial + 1

Cross-reference on Chainz Explorer

Block #1,695,985

Cookie Preferences