256639690 has 16 divisors (see below), whose sum is σ = 466715592. Its totient is φ = 101597184.

The previous prime is 256639673. The next prime is 256639697. The reversal of 256639690 is 96936652.

It can be written as a sum of positive squares in 4 ways, for example, as 112423609 + 144216081 = 10603^2 + 12009^2 .

It is a super-2 number, since 2×256639690² = 131727860966592200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 256639690.

It is not an unprimeable number, because it can be changed into a prime (256639697) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 131319 + ... + 133258.

Almost surely, 2^256639690 is an apocalyptic number.

256639690 is a deficient number, since it is larger than the sum of its proper divisors (210075902).

256639690 is a wasteful number, since it uses less digits than its factorization.

256639690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264681.

The product of its (nonzero) digits is 524880, while the sum is 46.

The square root of 256639690 is about 16019.9778401844. The cubic root of 256639690 is about 635.4888582650.

It can be divided in two parts, 25663 and 9690, that added together give a palindrome (35353).

The spelling of 256639690 in words is "two hundred fifty-six million, six hundred thirty-nine thousand, six hundred ninety".