21206164021 has 16 divisors (see below), whose sum is σ = 25677679104. Its totient is φ = 17096534784.

The previous prime is 21206164003. The next prime is 21206164039. The reversal of 21206164021 is 12046160212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21206164003) and next prime (21206164039).

It is not a de Polignac number, because 21206164021 - 2²¹ = 21204066869 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206164061) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 132091 + ... + 244663.

It is an arithmetic number, because the mean of its divisors is an integer number (1604854944).

Almost surely, 2^21206164021 is an apocalyptic number.

It is an amenable number.

21206164021 is a deficient number, since it is larger than the sum of its proper divisors (4471515083).

21206164021 is a wasteful number, since it uses less digits than its factorization.

21206164021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114180.

The product of its (nonzero) digits is 1152, while the sum is 25.

The spelling of 21206164021 in words is "twenty-one billion, two hundred six million, one hundred sixty-four thousand, twenty-one".