21015221502 has 16 divisors (see below), whose sum is σ = 45851392512. Its totient is φ = 6368248920.

The previous prime is 21015221477. The next prime is 21015221503. The reversal of 21015221502 is 20512251012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21015221503) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 159206158 + ... + 159206289.

It is an arithmetic number, because the mean of its divisors is an integer number (2865712032).

Almost surely, 2^21015221502 is an apocalyptic number.

21015221502 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21015221502 is an abundant number, since it is smaller than the sum of its proper divisors (24836171010).

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

21015221502 is a wasteful number, since it uses less digits than its factorization.

21015221502 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318412463.

The product of its (nonzero) digits is 400, while the sum is 21.

Adding to 21015221502 its reverse (20512251012), we get a palindrome (41527472514).

The spelling of 21015221502 in words is "twenty-one billion, fifteen million, two hundred twenty-one thousand, five hundred two".