21216565514655 has 64 divisors (see below), whose sum is σ = 43164073267200. Its totient is φ = 9686086272000.

The previous prime is 21216565514621. The next prime is 21216565514659. The reversal of 21216565514655 is 55641556561212.

21216565514655 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 6 + 5 + 65 + 514 + 65 + 5 = 666.

It is not a de Polignac number, because 21216565514655 - 2⁷ = 21216565514527 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216565514659) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 14237970 + ... + 15657359.

It is an arithmetic number, because the mean of its divisors is an integer number (674438644800).

Almost surely, 2^{21216565514655} is an apocalyptic number.

21216565514655 is an abundant number, since it is smaller than the sum of its proper divisors (21947507752545).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21216565514655 is a wasteful number, since it uses less digits than its factorization.

21216565514655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29896101 (or 29896095 counting only the distinct ones).

The product of its digits is 10800000, while the sum is 54.

The spelling of 21216565514655 in words is "twenty-one trillion, two hundred sixteen billion, five hundred sixty-five million, five hundred fourteen thousand, six hundred fifty-five".