21009935520 has 1152 divisors, whose sum is σ = 95103590400. Its totient is φ = 4263985152.

The previous prime is 21009935489. The next prime is 21009935581. The reversal of 21009935520 is 2553990012.

It is a happy number.

21009935520 is a `hidden beast` number, since 2 + 10 + 0 + 9 + 93 + 552 + 0 = 666.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 87907561 + ... + 87907799.

It is an arithmetic number, because the mean of its divisors is an integer number (82555200).

Almost surely, 2^21009935520 is an apocalyptic number.

21009935520 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 21009935520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47551795200).

21009935520 is an abundant number, since it is smaller than the sum of its proper divisors (74093654880).

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

21009935520 is a wasteful number, since it uses less digits than its factorization.

21009935520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312 (or 292 counting only the distinct ones).

The product of its (nonzero) digits is 24300, while the sum is 36.

The spelling of 21009935520 in words is "twenty-one billion, nine million, nine hundred thirty-five thousand, five hundred twenty".