256120981 has 2 divisors, whose sum is σ = 256120982. Its totient is φ = 256120980.

The previous prime is 256120961. The next prime is 256121023. The reversal of 256120981 is 189021652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 195748081 + 60372900 = 13991^2 + 7770^2 .

It is a cyclic number.

It is not a de Polignac number, because 256120981 - 2¹³ = 256112789 is a prime.

It is a super-2 number, since 2×256120981² = 131195913816804722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256120961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128060490 + 128060491.

It is an arithmetic number, because the mean of its divisors is an integer number (128060491).

Almost surely, 2^256120981 is an apocalyptic number.

It is an amenable number.

256120981 is a deficient number, since it is larger than the sum of its proper divisors (1).

256120981 is an equidigital number, since it uses as much as digits as its factorization.

256120981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8640, while the sum is 34.

The square root of 256120981 is about 16003.7802096880. The cubic root of 256120981 is about 635.0604286634.

The spelling of 256120981 in words is "two hundred fifty-six million, one hundred twenty thousand, nine hundred eighty-one".