21065580 has 72 divisors (see below), whose sum is σ = 65646672. Its totient is φ = 5463936.

The previous prime is 21065563. The next prime is 21065599. The reversal of 21065580 is 8556012.

21065580 is a `hidden beast` number, since 2 + 1 + 0 + 655 + 8 + 0 = 666.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 5079 + ... + 8241.

Almost surely, 2^21065580 is an apocalyptic number.

21065580 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21065580, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32823336).

21065580 is an abundant number, since it is smaller than the sum of its proper divisors (44581092).

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

21065580 is a wasteful number, since it uses less digits than its factorization.

21065580 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3215 (or 3210 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 27.

The square root of 21065580 is about 4589.7254819869. The cubic root of 21065580 is about 276.1793100727.

The spelling of 21065580 in words is "twenty-one million, sixty-five thousand, five hundred eighty".