21633937 has 16 divisors (see below), whose sum is σ = 24533712. Its totient is φ = 18938880.

The previous prime is 21633919. The next prime is 21633947. The reversal of 21633937 is 73933612.

It can be written as a sum of positive squares in 8 ways, for example, as 2702736 + 18931201 = 1644^2 + 4351^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21633937 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21633917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19173 + ... + 20269.

It is an arithmetic number, because the mean of its divisors is an integer number (1533357).

Almost surely, 2^21633937 is an apocalyptic number.

It is an amenable number.

21633937 is a deficient number, since it is larger than the sum of its proper divisors (2899775).

21633937 is a wasteful number, since it uses less digits than its factorization.

21633937 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1188.

The product of its digits is 20412, while the sum is 34.

The square root of 21633937 is about 4651.2296223687. The cubic root of 21633937 is about 278.6411070308.

The spelling of 21633937 in words is "twenty-one million, six hundred thirty-three thousand, nine hundred thirty-seven".