256648981 has 2 divisors, whose sum is σ = 256648982. Its totient is φ = 256648980.

The previous prime is 256648967. The next prime is 256649009. The reversal of 256648981 is 189846652.

256648981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 247558756 + 9090225 = 15734^2 + 3015^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256648981 is a prime.

It is a super-2 number, since 2×256648981² = 131737398896676722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256648901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128324490 + 128324491.

It is an arithmetic number, because the mean of its divisors is an integer number (128324491).

Almost surely, 2^256648981 is an apocalyptic number.

It is an amenable number.

256648981 is a deficient number, since it is larger than the sum of its proper divisors (1).

256648981 is an equidigital number, since it uses as much as digits as its factorization.

256648981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 829440, while the sum is 49.

The square root of 256648981 is about 16020.2678192345. The cubic root of 256648981 is about 635.4965269356.

The spelling of 256648981 in words is "two hundred fifty-six million, six hundred forty-eight thousand, nine hundred eighty-one".