21320197920 has 1296 divisors, whose sum is σ = 95618734848. Its totient is φ = 4467778560.

The previous prime is 21320197897. The next prime is 21320197937. The reversal of 21320197920 is 2979102312.

It is a tau number, because it is divible by the number of its divisors (1296).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 215 ways as a sum of consecutive naturals, for example, 687748305 + ... + 687748335.

It is an arithmetic number, because the mean of its divisors is an integer number (73779888).

Almost surely, 2^21320197920 is an apocalyptic number.

21320197920 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 21320197920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47809367424).

21320197920 is an abundant number, since it is smaller than the sum of its proper divisors (74298536928).

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

21320197920 is a wasteful number, since it uses less digits than its factorization.

21320197920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113 (or 67 counting only the distinct ones).

The product of its (nonzero) digits is 13608, while the sum is 36.

The spelling of 21320197920 in words is "twenty-one billion, three hundred twenty million, one hundred ninety-seven thousand, nine hundred twenty".