21015505252 has 12 divisors (see below), whose sum is σ = 42031010560. Its totient is φ = 9006645096.

The previous prime is 21015505249. The next prime is 21015505253. The reversal of 21015505252 is 25250551012.

21015505252 is an admirable number.

It is a Harshad number since it is a multiple of its sum of digits (28), and also a Moran number because the ratio is a prime number: 750553759 = 21015505252 / (2 + 1 + 0 + 1 + 5 + 5 + 0 + 5 + 2 + 5 + 2).

It is a self number, because there is not a number n which added to its sum of digits gives 21015505252.

It is not an unprimeable number, because it can be changed into a prime (21015505253) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 375276852 + ... + 375276907.

Almost surely, 2^21015505252 is an apocalyptic number.

It is an amenable number.

21015505252 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21015505252 is a wasteful number, since it uses less digits than its factorization.

21015505252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 750553770 (or 750553768 counting only the distinct ones).

The product of its (nonzero) digits is 5000, while the sum is 28.

The spelling of 21015505252 in words is "twenty-one billion, fifteen million, five hundred five thousand, two hundred fifty-two".