256263659921 has 2 divisors, whose sum is σ = 256263659922. Its totient is φ = 256263659920.

The previous prime is 256263659903. The next prime is 256263660019. The reversal of 256263659921 is 129956362652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 197620257025 + 58643402896 = 444545^2 + 242164^2 .

It is a cyclic number.

It is not a de Polignac number, because 256263659921 - 2¹⁸ = 256263397777 is a prime.

It is a super-2 number, since 2×256263659921² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (256263659321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128131829960 + 128131829961.

It is an arithmetic number, because the mean of its divisors is an integer number (128131829961).

Almost surely, 2^256263659921 is an apocalyptic number.

It is an amenable number.

256263659921 is a deficient number, since it is larger than the sum of its proper divisors (1).

256263659921 is an equidigital number, since it uses as much as digits as its factorization.

256263659921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10497600, while the sum is 56.

The spelling of 256263659921 in words is "two hundred fifty-six billion, two hundred sixty-three million, six hundred fifty-nine thousand, nine hundred twenty-one".