256621012371621 has 6 divisors (see below), whose sum is σ = 370674795647910. Its totient is φ = 171080674914408.

The previous prime is 256621012371611. The next prime is 256621012371751. The reversal of 256621012371621 is 126173210126652.

256621012371621 is a `hidden beast` number, since 2 + 5 + 6 + 6 + 2 + 1 + 0 + 12 + 3 + 7 + 1 + 621 = 666.

It can be written as a sum of positive squares in only one way, i.e., 246398508891396 + 10222503480225 = 15697086^2 + 3197265^2 .

It is not a de Polignac number, because 256621012371621 - 2³⁵ = 256586652633253 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256621012371601) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 14256722909526 + ... + 14256722909543.

It is an arithmetic number, because the mean of its divisors is an integer number (61779132607985).

Almost surely, 2^{256621012371621} is an apocalyptic number.

It is an amenable number.

256621012371621 is a deficient number, since it is larger than the sum of its proper divisors (114053783276289).

256621012371621 is a wasteful number, since it uses less digits than its factorization.

256621012371621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28513445819075 (or 28513445819072 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 45.

The spelling of 256621012371621 in words is "two hundred fifty-six trillion, six hundred twenty-one billion, twelve million, three hundred seventy-one thousand, six hundred twenty-one".