21500557420 has 24 divisors (see below), whose sum is σ = 45207855504. Its totient is φ = 8589425856.

The previous prime is 21500557417. The next prime is 21500557459. The reversal of 21500557420 is 2475500512.

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 7 ways as a sum of consecutive naturals, for example, 658482 + ... + 690361.

It is an arithmetic number, because the mean of its divisors is an integer number (1883660646).

Almost surely, 2^21500557420 is an apocalyptic number.

21500557420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21500557420 is an abundant number, since it is smaller than the sum of its proper divisors (23707298084).

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

21500557420 is a wasteful number, since it uses less digits than its factorization.

21500557420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1349649 (or 1349647 counting only the distinct ones).

The product of its (nonzero) digits is 14000, while the sum is 31.

The spelling of 21500557420 in words is "twenty-one billion, five hundred million, five hundred fifty-seven thousand, four hundred twenty".