21638874 has 16 divisors (see below), whose sum is σ = 43499808. Its totient is φ = 7175952.

The previous prime is 21638873. The next prime is 21638887. The reversal of 21638874 is 47883612.

It is not an unprimeable number, because it can be changed into a prime (21638873) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 7972 + ... + 10335.

It is an arithmetic number, because the mean of its divisors is an integer number (2718738).

Almost surely, 2^21638874 is an apocalyptic number.

21638874 is an abundant number, since it is smaller than the sum of its proper divisors (21860934).

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

21638874 is a wasteful number, since it uses less digits than its factorization.

21638874 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18509.

The product of its digits is 64512, while the sum is 39.

The square root of 21638874 is about 4651.7603119679. The cubic root of 21638874 is about 278.6623013009.

The spelling of 21638874 in words is "twenty-one million, six hundred thirty-eight thousand, eight hundred seventy-four".