256220661 has 4 divisors (see below), whose sum is σ = 341627552. Its totient is φ = 170813772.

The previous prime is 256220633. The next prime is 256220669. The reversal of 256220661 is 166022652.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 256220661 - 2¹⁰ = 256219637 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256220669) 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, 42703441 + ... + 42703446.

It is an arithmetic number, because the mean of its divisors is an integer number (85406888).

Almost surely, 2^256220661 is an apocalyptic number.

It is an amenable number.

256220661 is a deficient number, since it is larger than the sum of its proper divisors (85406891).

256220661 is an equidigital number, since it uses as much as digits as its factorization.

256220661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85406890.

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 256220661 is about 16006.8941709502. The cubic root of 256220661 is about 635.1428045947.

The spelling of 256220661 in words is "two hundred fifty-six million, two hundred twenty thousand, six hundred sixty-one".