21621621165 has 16 divisors (see below), whose sum is σ = 34607419776. Its totient is φ = 11527256000.

The previous prime is 21621621149. The next prime is 21621621187. The reversal of 21621621165 is 56112612612.

It is not a de Polignac number, because 21621621165 - 2⁴ = 21621621149 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 225186 + ... + 306515.

It is an arithmetic number, because the mean of its divisors is an integer number (2162963736).

Almost surely, 2^21621621165 is an apocalyptic number.

It is an amenable number.

21621621165 is a deficient number, since it is larger than the sum of its proper divisors (12985798611).

21621621165 is a wasteful number, since it uses less digits than its factorization.

21621621165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 534420.

The product of its digits is 8640, while the sum is 33.

The spelling of 21621621165 in words is "twenty-one billion, six hundred twenty-one million, six hundred twenty-one thousand, one hundred sixty-five".