256621 has 4 divisors (see below), whose sum is σ = 265500. Its totient is φ = 247744.

The previous prime is 256609. The next prime is 256639. The reversal of 256621 is 126652.

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 44100 + 212521 = 210^2 + 461^2 .

It is a cyclic number.

It is not a de Polignac number, because 256621 - 2⁵ = 256589 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 256592 and 256601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256651) 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, 4396 + ... + 4453.

It is an arithmetic number, because the mean of its divisors is an integer number (66375).

2²⁵⁶⁶²¹ is an apocalyptic number.

It is an amenable number.

256621 is a deficient number, since it is larger than the sum of its proper divisors (8879).

256621 is an equidigital number, since it uses as much as digits as its factorization.

256621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8878.

The product of its digits is 720, while the sum is 22.

The square root of 256621 is about 506.5777334230. The cubic root of 256621 is about 63.5473431221.

The spelling of 256621 in words is "two hundred fifty-six thousand, six hundred twenty-one".