21565672 has 32 divisors (see below), whose sum is σ = 42565320. Its totient is φ = 10229760.

The previous prime is 21565667. The next prime is 21565699. The reversal of 21565672 is 27656512.

It can be written as a sum of positive squares in 4 ways, for example, as 17589636 + 3976036 = 4194^2 + 1994^2 .

It is a super-3 number, since 3×21565672³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11248 + ... + 13024.

Almost surely, 2^21565672 is an apocalyptic number.

It is an amenable number.

21565672 is a deficient number, since it is larger than the sum of its proper divisors (20999648).

21565672 is a wasteful number, since it uses less digits than its factorization.

21565672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1861 (or 1857 counting only the distinct ones).

The product of its digits is 25200, while the sum is 34.

The square root of 21565672 is about 4643.8854421702. The cubic root of 21565672 is about 278.3477180306.

It can be divided in two parts, 2156567 and 2, that multiplied together give a palindrome (4313134).

The spelling of 21565672 in words is "twenty-one million, five hundred sixty-five thousand, six hundred seventy-two".