21661264621 has 8 divisors (see below), whose sum is σ = 22815378080. Its totient is φ = 20508555888.

The previous prime is 21661264613. The next prime is 21661264693. The reversal of 21661264621 is 12646216612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21661264621 - 2³ = 21661264613 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 (21661264421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 319446 + ... + 381271.

It is an arithmetic number, because the mean of its divisors is an integer number (2851922260).

Almost surely, 2^21661264621 is an apocalyptic number.

It is an amenable number.

21661264621 is a deficient number, since it is larger than the sum of its proper divisors (1154113459).

21661264621 is a wasteful number, since it uses less digits than its factorization.

21661264621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 702363.

The product of its digits is 41472, while the sum is 37.

The spelling of 21661264621 in words is "twenty-one billion, six hundred sixty-one million, two hundred sixty-four thousand, six hundred twenty-one".