21642642 has 48 divisors (see below), whose sum is σ = 55448640. Its totient is φ = 5969376.

The previous prime is 21642637. The next prime is 21642667. The reversal of 21642642 is 24624612.

21642642 is a `hidden beast` number, since 2 + 16 + 4 + 2 + 642 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 693 + ... + 6615.

It is an arithmetic number, because the mean of its divisors is an integer number (1155180).

Almost surely, 2^21642642 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21642642, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27724320).

21642642 is an abundant number, since it is smaller than the sum of its proper divisors (33805998).

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

21642642 is a wasteful number, since it uses less digits than its factorization.

21642642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5967 (or 5964 counting only the distinct ones).

The product of its digits is 4608, while the sum is 27.

The square root of 21642642 is about 4652.1653023082. The cubic root of 21642642 is about 278.6784749492.

The spelling of 21642642 in words is "twenty-one million, six hundred forty-two thousand, six hundred forty-two".