256997731 has 2 divisors, whose sum is σ = 256997732. Its totient is φ = 256997730.

The previous prime is 256997723. The next prime is 256997749. The reversal of 256997731 is 137799652.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 256997731 - 2³ = 256997723 is a prime.

It is a super-2 number, since 2×256997731² = 132095667478296722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (256997761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128498865 + 128498866.

It is an arithmetic number, because the mean of its divisors is an integer number (128498866).

Almost surely, 2^256997731 is an apocalyptic number.

256997731 is a deficient number, since it is larger than the sum of its proper divisors (1).

256997731 is an equidigital number, since it uses as much as digits as its factorization.

256997731 is an evil number, because the sum of its binary digits is even.

The product of its digits is 714420, while the sum is 49.

The square root of 256997731 is about 16031.1487735596. The cubic root of 256997731 is about 635.7842468931.

The spelling of 256997731 in words is "two hundred fifty-six million, nine hundred ninety-seven thousand, seven hundred thirty-one".