256309661 has 4 divisors (see below), whose sum is σ = 257184732. Its totient is φ = 255434592.

The previous prime is 256309657. The next prime is 256309679. The reversal of 256309661 is 166903652.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 230857636 + 25452025 = 15194^2 + 5045^2 .

It is a cyclic number.

It is not a de Polignac number, because 256309661 - 2² = 256309657 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256303661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 437096 + ... + 437681.

It is an arithmetic number, because the mean of its divisors is an integer number (64296183).

Almost surely, 2^256309661 is an apocalyptic number.

It is an amenable number.

256309661 is a deficient number, since it is larger than the sum of its proper divisors (875071).

256309661 is an equidigital number, since it uses as much as digits as its factorization.

256309661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875070.

The product of its (nonzero) digits is 58320, while the sum is 38.

The square root of 256309661 is about 16009.6739816899. The cubic root of 256309661 is about 635.2163364813.

The spelling of 256309661 in words is "two hundred fifty-six million, three hundred nine thousand, six hundred sixty-one".