21731638 has 4 divisors (see below), whose sum is σ = 32597460. Its totient is φ = 10865818.

The previous prime is 21731623. The next prime is 21731653. The reversal of 21731638 is 83613712.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21731623) and next prime (21731653).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5432908 + ... + 5432911.

It is an arithmetic number, because the mean of its divisors is an integer number (8149365).

Almost surely, 2^21731638 is an apocalyptic number.

21731638 is a deficient number, since it is larger than the sum of its proper divisors (10865822).

21731638 is a wasteful number, since it uses less digits than its factorization.

21731638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10865821.

The product of its digits is 6048, while the sum is 31.

The square root of 21731638 is about 4661.7204978420. The cubic root of 21731638 is about 279.0599341101.

The spelling of 21731638 in words is "twenty-one million, seven hundred thirty-one thousand, six hundred thirty-eight".