21657642 has 16 divisors (see below), whose sum is σ = 43447872. Its totient is φ = 7197120.

The previous prime is 21657641. The next prime is 21657653. The reversal of 21657642 is 24675612.

It is not an unprimeable number, because it can be changed into a prime (21657641) 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 7 ways as a sum of consecutive naturals, for example, 3334 + ... + 7377.

It is an arithmetic number, because the mean of its divisors is an integer number (2715492).

Almost surely, 2^21657642 is an apocalyptic number.

21657642 is an abundant number, since it is smaller than the sum of its proper divisors (21790230).

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

21657642 is a wasteful number, since it uses less digits than its factorization.

21657642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11053.

The product of its digits is 20160, while the sum is 33.

The square root of 21657642 is about 4653.7771755854. Note that the first 3 decimals coincide. The cubic root of 21657642 is about 278.7428418869.

The spelling of 21657642 in words is "twenty-one million, six hundred fifty-seven thousand, six hundred forty-two".