21206797920 has 960 divisors, whose sum is σ = 94842316800. Its totient is φ = 4334653440.

The previous prime is 21206797903. The next prime is 21206797943. The reversal of 21206797920 is 2979760212.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 78835546 + ... + 78835814.

It is an arithmetic number, because the mean of its divisors is an integer number (98794080).

Almost surely, 2^21206797920 is an apocalyptic number.

21206797920 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 21206797920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47421158400).

21206797920 is an abundant number, since it is smaller than the sum of its proper divisors (73635518880).

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

21206797920 is a wasteful number, since it uses less digits than its factorization.

21206797920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 393 (or 376 counting only the distinct ones).

The product of its (nonzero) digits is 190512, while the sum is 45.

The spelling of 21206797920 in words is "twenty-one billion, two hundred six million, seven hundred ninety-seven thousand, nine hundred twenty".