21691580 has 12 divisors (see below), whose sum is σ = 45552360. Its totient is φ = 8676624.

The previous prime is 21691577. The next prime is 21691613. The reversal of 21691580 is 8519612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 542270 + ... + 542309.

It is an arithmetic number, because the mean of its divisors is an integer number (3796030).

Almost surely, 2^21691580 is an apocalyptic number.

21691580 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21691580 is an abundant number, since it is smaller than the sum of its proper divisors (23860780).

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

21691580 is a wasteful number, since it uses less digits than its factorization.

21691580 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1084588 (or 1084586 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 21691580 is about 4657.4220337006. The cubic root of 21691580 is about 278.8883646164. Note that the first 3 decimals are identical.

The spelling of 21691580 in words is "twenty-one million, six hundred ninety-one thousand, five hundred eighty".