21667638 has 32 divisors (see below), whose sum is σ = 46275840. Its totient is φ = 6743520.

The previous prime is 21667603. The next prime is 21667649. The reversal of 21667638 is 83676612.

It is a junction number, because it is equal to n+sod(n) for n = 21667596 and 21667605.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6756 + ... + 9432.

It is an arithmetic number, because the mean of its divisors is an integer number (1446120).

Almost surely, 2^21667638 is an apocalyptic number.

21667638 is an abundant number, since it is smaller than the sum of its proper divisors (24608202).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21667638 is a wasteful number, since it uses less digits than its factorization.

21667638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2772.

The product of its digits is 72576, while the sum is 39.

The square root of 21667638 is about 4654.8510180241. The cubic root of 21667638 is about 278.7857195139.

The spelling of 21667638 in words is "twenty-one million, six hundred sixty-seven thousand, six hundred thirty-eight".