256621617 has 12 divisors (see below), whose sum is σ = 423629440. Its totient is φ = 146640888.

The previous prime is 256621577. The next prime is 256621633. The reversal of 256621617 is 716126652.

It is a happy number.

256621617 is a `hidden beast` number, since 25 + 6 + 621 + 6 + 1 + 7 = 666.

It is not a de Polignac number, because 256621617 - 2¹² = 256617521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256621117) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2036617 + ... + 2036742.

Almost surely, 2^256621617 is an apocalyptic number.

It is an amenable number.

256621617 is a deficient number, since it is larger than the sum of its proper divisors (167007823).

256621617 is a wasteful number, since it uses less digits than its factorization.

256621617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4073372 (or 4073369 counting only the distinct ones).

The product of its digits is 30240, while the sum is 36.

The square root of 256621617 is about 16019.4137533182. The cubic root of 256621617 is about 635.4739405156.

The spelling of 256621617 in words is "two hundred fifty-six million, six hundred twenty-one thousand, six hundred seventeen".