21164490 has 160 divisors (see below), whose sum is σ = 63510480. Its totient is φ = 5031936.

The previous prime is 21164489. The next prime is 21164501. The reversal of 21164490 is 9446112.

21164490 is a `hidden beast` number, since 2 + 11 + 644 + 9 + 0 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 14768649 + 6395841 = 3843^2 + 2529^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 399304 + ... + 399356.

Almost surely, 2^21164490 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21164490, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31755240).

21164490 is an abundant number, since it is smaller than the sum of its proper divisors (42345990).

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

21164490 is a wasteful number, since it uses less digits than its factorization.

21164490 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118 (or 109 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21164490 is about 4600.4880175912. The cubic root of 21164490 is about 276.6108869661.

The spelling of 21164490 in words is "twenty-one million, one hundred sixty-four thousand, four hundred ninety".