21115515515020 has 96 divisors (see below), whose sum is σ = 44721604287360. Its totient is φ = 8374346956800.

The previous prime is 21115515515009. The next prime is 21115515515027. The reversal of 21115515515020 is 2051551551112.

It is not an unprimeable number, because it can be changed into a prime (21115515515027) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1716562870 + ... + 1716575170.

It is an arithmetic number, because the mean of its divisors is an integer number (465850044660).

Almost surely, 2^{21115515515020} is an apocalyptic number.

21115515515020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21115515515020 is an abundant number, since it is smaller than the sum of its proper divisors (23606088772340).

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

21115515515020 is a wasteful number, since it uses less digits than its factorization.

21115515515020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13955 (or 13953 counting only the distinct ones).

The product of its (nonzero) digits is 12500, while the sum is 34.

The spelling of 21115515515020 in words is "twenty-one trillion, one hundred fifteen billion, five hundred fifteen million, five hundred fifteen thousand, twenty".