20891951520 has 384 divisors, whose sum is σ = 74851983360. Its totient is φ = 4852224000.

The previous prime is 20891951503. The next prime is 20891951539. The reversal of 20891951520 is 2515919802.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 17840535 + ... + 17841705.

It is an arithmetic number, because the mean of its divisors is an integer number (194927040).

Almost surely, 2^20891951520 is an apocalyptic number.

20891951520 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 20891951520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37425991680).

20891951520 is an abundant number, since it is smaller than the sum of its proper divisors (53960031840).

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

20891951520 is a wasteful number, since it uses less digits than its factorization.

20891951520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1340 (or 1332 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 42.

The spelling of 20891951520 in words is "twenty billion, eight hundred ninety-one million, nine hundred fifty-one thousand, five hundred twenty".