21038657436961 has 4 divisors (see below), whose sum is σ = 21105025441812. Its totient is φ = 20972289432112.

The previous prime is 21038657436919. The next prime is 21038657437087. The reversal of 21038657436961 is 16963475683012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10141957406736 + 10896700030225 = 3184644^2 + 3301015^2 .

It is a cyclic number.

It is not a de Polignac number, because 21038657436961 - 2¹³ = 21038657428769 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21038657436961.

It is not an unprimeable number, because it can be changed into a prime (21038657433961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33184001950 + ... + 33184002583.

It is an arithmetic number, because the mean of its divisors is an integer number (5276256360453).

It is a 1-persistent number, because it is pandigital, but 2⋅21038657436961 = 42077314873922 is not.

Almost surely, 2^{21038657436961} is an apocalyptic number.

It is an amenable number.

21038657436961 is a deficient number, since it is larger than the sum of its proper divisors (66368004851).

21038657436961 is an equidigital number, since it uses as much as digits as its factorization.

21038657436961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66368004850.

The product of its (nonzero) digits is 39191040, while the sum is 61.

The spelling of 21038657436961 in words is "twenty-one trillion, thirty-eight billion, six hundred fifty-seven million, four hundred thirty-six thousand, nine hundred sixty-one".