21520371620 has 96 divisors (see below), whose sum is σ = 51094471680. Its totient is φ = 7541936640.

The previous prime is 21520371601. The next prime is 21520371643. The reversal of 21520371620 is 2617302512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 3869882 + ... + 3875438.

It is an arithmetic number, because the mean of its divisors is an integer number (532234080).

Almost surely, 2^21520371620 is an apocalyptic number.

21520371620 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 21520371620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25547235840).

21520371620 is an abundant number, since it is smaller than the sum of its proper divisors (29574100060).

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

21520371620 is a wasteful number, since it uses less digits than its factorization.

21520371620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6213 (or 6211 counting only the distinct ones).

The product of its (nonzero) digits is 5040, while the sum is 29.

The spelling of 21520371620 in words is "twenty-one billion, five hundred twenty million, three hundred seventy-one thousand, six hundred twenty".