21402179810021 has 2 divisors, whose sum is σ = 21402179810022. Its totient is φ = 21402179810020.

The previous prime is 21402179809949. The next prime is 21402179810239. The reversal of 21402179810021 is 12001897120412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19711477737121 + 1690702072900 = 4439761^2 + 1300270^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21402179810021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21402179810621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701089905010 + 10701089905011.

It is an arithmetic number, because the mean of its divisors is an integer number (10701089905011).

Almost surely, 2^{21402179810021} is an apocalyptic number.

It is an amenable number.

21402179810021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21402179810021 is an equidigital number, since it uses as much as digits as its factorization.

21402179810021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 38.

The spelling of 21402179810021 in words is "twenty-one trillion, four hundred two billion, one hundred seventy-nine million, eight hundred ten thousand, twenty-one".