21210656121 has 12 divisors (see below), whose sum is σ = 30639681072. Its totient is φ = 14139483576.

The previous prime is 21210656107. The next prime is 21210656171. The reversal of 21210656121 is 12165601212.

21210656121 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 0 + 656 + 1 + 2 + 1 = 666.

It is not a de Polignac number, because 21210656121 - 2²⁵ = 21177101689 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21210656171) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 77710 + ... + 220136.

It is an arithmetic number, because the mean of its divisors is an integer number (2553306756).

Almost surely, 2^21210656121 is an apocalyptic number.

It is an amenable number.

21210656121 is a deficient number, since it is larger than the sum of its proper divisors (9429024951).

21210656121 is a wasteful number, since it uses less digits than its factorization.

21210656121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158980 (or 158977 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The spelling of 21210656121 in words is "twenty-one billion, two hundred ten million, six hundred fifty-six thousand, one hundred twenty-one".