256990381 has 2 divisors, whose sum is σ = 256990382. Its totient is φ = 256990380.

The previous prime is 256990369. The next prime is 256990399. The reversal of 256990381 is 183099652.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 226021156 + 30969225 = 15034^2 + 5565^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256990381 is a prime.

It is a super-2 number, since 2×256990381² = 132088111853050322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256990301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128495190 + 128495191.

It is an arithmetic number, because the mean of its divisors is an integer number (128495191).

Almost surely, 2^256990381 is an apocalyptic number.

It is an amenable number.

256990381 is a deficient number, since it is larger than the sum of its proper divisors (1).

256990381 is an equidigital number, since it uses as much as digits as its factorization.

256990381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 116640, while the sum is 43.

The square root of 256990381 is about 16030.9195307069. The cubic root of 256990381 is about 635.7781858036.

The spelling of 256990381 in words is "two hundred fifty-six million, nine hundred ninety thousand, three hundred eighty-one".