21661032164021 has 4 divisors (see below), whose sum is σ = 22164777098112. Its totient is φ = 21157287229932.

The previous prime is 21661032164017. The next prime is 21661032164027. The reversal of 21661032164021 is 12046123016612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21661032164021 - 2² = 21661032164017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661032164027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 251872466981 + ... + 251872467066.

It is an arithmetic number, because the mean of its divisors is an integer number (5541194274528).

Almost surely, 2^{21661032164021} is an apocalyptic number.

It is an amenable number.

21661032164021 is a deficient number, since it is larger than the sum of its proper divisors (503744934091).

21661032164021 is an equidigital number, since it uses as much as digits as its factorization.

21661032164021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 503744934090.

The product of its (nonzero) digits is 20736, while the sum is 35.

The spelling of 21661032164021 in words is "twenty-one trillion, six hundred sixty-one billion, thirty-two million, one hundred sixty-four thousand, twenty-one".