21566216 has 32 divisors (see below), whose sum is σ = 48648000. Its totient is φ = 8755776.

The previous prime is 21566201. The next prime is 21566219. The reversal of 21566216 is 61266512.

It is not an unprimeable number, because it can be changed into a prime (21566219) 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, 9071 + ... + 11198.

It is an arithmetic number, because the mean of its divisors is an integer number (1520250).

Almost surely, 2^21566216 is an apocalyptic number.

It is an amenable number.

21566216 is an abundant number, since it is smaller than the sum of its proper divisors (27081784).

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

21566216 is a wasteful number, since it uses less digits than its factorization.

21566216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20301 (or 20297 counting only the distinct ones).

The product of its digits is 4320, while the sum is 29.

The square root of 21566216 is about 4643.9440134437. The cubic root of 21566216 is about 278.3500584768.

The spelling of 21566216 in words is "twenty-one million, five hundred sixty-six thousand, two hundred sixteen".