21115215520 has 96 divisors (see below), whose sum is σ = 58977072000. Its totient is φ = 6989853696.

The previous prime is 21115215497. The next prime is 21115215523. The reversal of 21115215520 is 2551251112.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21115215523) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 292570 + ... + 357529.

It is an arithmetic number, because the mean of its divisors is an integer number (614344500).

Almost surely, 2^21115215520 is an apocalyptic number.

21115215520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21115215520 is an abundant number, since it is smaller than the sum of its proper divisors (37861856480).

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

21115215520 is a wasteful number, since it uses less digits than its factorization.

21115215520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 650150 (or 650142 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 25.

Adding to 21115215520 its reverse (2551251112), we get a palindrome (23666466632).

The spelling of 21115215520 in words is "twenty-one billion, one hundred fifteen million, two hundred fifteen thousand, five hundred twenty".