21520687500 has 504 divisors, whose sum is σ = 76638081520. Its totient is φ = 5248800000.

The previous prime is 21520687483. The next prime is 21520687571. The reversal of 21520687500 is 578602512.

It is a happy number.

21520687500 is a `hidden beast` number, since 2 + 1 + 520 + 6 + 87 + 50 + 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 polite number, since it can be written in 167 ways as a sum of consecutive naturals, for example, 197437446 + ... + 197437554.

Almost surely, 2^21520687500 is an apocalyptic number.

21520687500 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 21520687500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38319040760).

21520687500 is an abundant number, since it is smaller than the sum of its proper divisors (55117394020).

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

21520687500 is an equidigital number, since it uses as much as digits as its factorization.

21520687500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171 (or 132 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

The spelling of 21520687500 in words is "twenty-one billion, five hundred twenty million, six hundred eighty-seven thousand, five hundred".