21556965 has 16 divisors (see below), whose sum is σ = 34609536. Its totient is φ = 11457600.

The previous prime is 21556961. The next prime is 21556979. The reversal of 21556965 is 56965512.

It is not a de Polignac number, because 21556965 - 2² = 21556961 is a prime.

It is a super-2 number, since 2×21556965² = 929405480022450, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21556961) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2355 + ... + 6975.

It is an arithmetic number, because the mean of its divisors is an integer number (2163096).

Almost surely, 2^21556965 is an apocalyptic number.

It is an amenable number.

21556965 is a deficient number, since it is larger than the sum of its proper divisors (13052571).

21556965 is a wasteful number, since it uses less digits than its factorization.

21556965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4940.

The product of its digits is 81000, while the sum is 39.

The square root of 21556965 is about 4642.9478782343. The cubic root of 21556965 is about 278.3102526269.

The spelling of 21556965 in words is "twenty-one million, five hundred fifty-six thousand, nine hundred sixty-five".