21537956 has 24 divisors (see below), whose sum is σ = 42124320. Its totient is φ = 9550400.

The previous prime is 21537937. The next prime is 21537961. The reversal of 21537956 is 65973512.

It is a happy number.

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, 4166 + ... + 7773.

It is an arithmetic number, because the mean of its divisors is an integer number (1755180).

Almost surely, 2^21537956 is an apocalyptic number.

It is an amenable number.

21537956 is a deficient number, since it is larger than the sum of its proper divisors (20586364).

21537956 is a wasteful number, since it uses less digits than its factorization.

21537956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11995 (or 11993 counting only the distinct ones).

The product of its digits is 56700, while the sum is 38.

The square root of 21537956 is about 4640.9003436833. The cubic root of 21537956 is about 278.2284236158.

Subtracting 21537956 from its reverse (65973512), we obtain a square (44435556 = 6666²).

The spelling of 21537956 in words is "twenty-one million, five hundred thirty-seven thousand, nine hundred fifty-six".