21658920780 has 48 divisors (see below), whose sum is σ = 69308547840. Its totient is φ = 4950610368.

The previous prime is 21658920749. The next prime is 21658920797. The reversal of 21658920780 is 8702985612.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25784010 + ... + 25784849.

It is an arithmetic number, because the mean of its divisors is an integer number (1443928080).

Almost surely, 2^21658920780 is an apocalyptic number.

21658920780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21658920780 is an abundant number, since it is smaller than the sum of its proper divisors (47649627060).

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

21658920780 is a wasteful number, since it uses less digits than its factorization.

21658920780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51568878 (or 51568876 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 48.

The spelling of 21658920780 in words is "twenty-one billion, six hundred fifty-eight million, nine hundred twenty thousand, seven hundred eighty".