21631939 has 20 divisors (see below), whose sum is σ = 26977264. Its totient is φ = 16979328.

The previous prime is 21631921. The next prime is 21631949. The reversal of 21631939 is 93913612.

It is a de Polignac number, because none of the positive numbers 2^k-21631939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21631949) 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 19 ways as a sum of consecutive naturals, for example, 584629 + ... + 584665.

Almost surely, 2^21631939 is an apocalyptic number.

21631939 is a deficient number, since it is larger than the sum of its proper divisors (5345325).

21631939 is an frugal number, since it uses more digits than its factorization.

21631939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112 (or 61 counting only the distinct ones).

The product of its digits is 8748, while the sum is 34.

The square root of 21631939 is about 4651.0148354956. The cubic root of 21631939 is about 278.6325288099.

The spelling of 21631939 in words is "twenty-one million, six hundred thirty-one thousand, nine hundred thirty-nine".