21331991520 has 480 divisors, whose sum is σ = 87887213568. Its totient is φ = 4771187712.

The previous prime is 21331991509. The next prime is 21331991533. The reversal of 21331991520 is 2519913312.

21331991520 is a `hidden beast` number, since 2 + 1 + 33 + 19 + 91 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (480).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 4261339 + ... + 4266341.

Almost surely, 2^21331991520 is an apocalyptic number.

21331991520 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 21331991520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43943606784).

21331991520 is an abundant number, since it is smaller than the sum of its proper divisors (66555222048).

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

21331991520 is a wasteful number, since it uses less digits than its factorization.

21331991520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5084 (or 5067 counting only the distinct ones).

The product of its (nonzero) digits is 14580, while the sum is 36.

The spelling of 21331991520 in words is "twenty-one billion, three hundred thirty-one million, nine hundred ninety-one thousand, five hundred twenty".