21315124520 has 16 divisors (see below), whose sum is σ = 47959030260. Its totient is φ = 8526049792.

The previous prime is 21315124513. The next prime is 21315124541. The reversal of 21315124520 is 2542151312.

It can be written as a sum of positive squares in 2 ways, for example, as 19699245316 + 1615879204 = 140354^2 + 40198^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21315124520.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 266439017 + ... + 266439096.

Almost surely, 2^21315124520 is an apocalyptic number.

21315124520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21315124520 is an abundant number, since it is smaller than the sum of its proper divisors (26643905740).

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

21315124520 is a wasteful number, since it uses less digits than its factorization.

21315124520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 532878124 (or 532878120 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 26.

Adding to 21315124520 its reverse (2542151312), we get a palindrome (23857275832).

The spelling of 21315124520 in words is "twenty-one billion, three hundred fifteen million, one hundred twenty-four thousand, five hundred twenty".