21644490 has 32 divisors (see below), whose sum is σ = 59368320. Its totient is φ = 4947264.

The previous prime is 21644489. The next prime is 21644507. The reversal of 21644490 is 9444612.

It is a Harshad number since it is a multiple of its sum of digits (30).

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, 51325 + ... + 51744.

It is an arithmetic number, because the mean of its divisors is an integer number (1855260).

Almost surely, 2^21644490 is an apocalyptic number.

21644490 is an abundant number, since it is smaller than the sum of its proper divisors (37723830).

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

21644490 is a wasteful number, since it uses less digits than its factorization.

21644490 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 103086.

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 21644490 is about 4652.3639152586. The cubic root of 21644490 is about 278.6864065619.

The spelling of 21644490 in words is "twenty-one million, six hundred forty-four thousand, four hundred ninety".