Block #281,890

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.

1.709 × 10⁹⁶(97-digit number)

17095383168620082804…78403947602694497279

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

1.709 × 10⁹⁶(97-digit number)

17095383168620082804…78403947602694497279

Verify on FactorDB ↗Wolfram Alpha ↗

origin + 1

1.709 × 10⁹⁶(97-digit number)

17095383168620082804…78403947602694497281

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

3.419 × 10⁹⁶(97-digit number)

34190766337240165609…56807895205388994559

Verify on FactorDB ↗Wolfram Alpha ↗

2^1 × origin + 1

3.419 × 10⁹⁶(97-digit number)

34190766337240165609…56807895205388994561

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

6.838 × 10⁹⁶(97-digit number)

68381532674480331218…13615790410777989119

Verify on FactorDB ↗Wolfram Alpha ↗

2^2 × origin + 1

6.838 × 10⁹⁶(97-digit number)

68381532674480331218…13615790410777989121

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

1.367 × 10⁹⁷(98-digit number)

13676306534896066243…27231580821555978239

Verify on FactorDB ↗Wolfram Alpha ↗

2^3 × origin + 1

1.367 × 10⁹⁷(98-digit number)

13676306534896066243…27231580821555978241

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

2.735 × 10⁹⁷(98-digit number)

27352613069792132487…54463161643111956479

Verify on FactorDB ↗Wolfram Alpha ↗

What this block proved

The miner who found this block proved the existence of 9 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

CommonChain length 9

Found in most blocks. The baseline for Primecoin's proof-of-work.

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