21015666580 has 24 divisors (see below), whose sum is σ = 44276668128. Its totient is φ = 8378882208.

The previous prime is 21015666571. The next prime is 21015666589. The reversal of 21015666580 is 8566651012.

It is an interprime number because it is at equal distance from previous prime (21015666571) and next prime (21015666589).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21015666589) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1705234 + ... + 1717513.

It is an arithmetic number, because the mean of its divisors is an integer number (1844861172).

Almost surely, 2^21015666580 is an apocalyptic number.

21015666580 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21015666580 is an abundant number, since it is smaller than the sum of its proper divisors (23261001548).

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

21015666580 is a wasteful number, since it uses less digits than its factorization.

21015666580 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3423063 (or 3423061 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 40.

The spelling of 21015666580 in words is "twenty-one billion, fifteen million, six hundred sixty-six thousand, five hundred eighty".