21151511525 has 24 divisors (see below), whose sum is σ = 26879920200. Its totient is φ = 16500915200.

The previous prime is 21151511461. The next prime is 21151511561. The reversal of 21151511525 is 52511515112.

It can be written as a sum of positive squares in 12 ways, for example, as 7858113316 + 13293398209 = 88646^2 + 115297^2 .

It is not a de Polignac number, because 21151511525 - 2⁶ = 21151511461 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3470681 + ... + 3476769.

It is an arithmetic number, because the mean of its divisors is an integer number (1119996675).

Almost surely, 2^21151511525 is an apocalyptic number.

21151511525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21151511525 is a deficient number, since it is larger than the sum of its proper divisors (5728408675).

21151511525 is a wasteful number, since it uses less digits than its factorization.

21151511525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9529 (or 9524 counting only the distinct ones).

The product of its digits is 2500, while the sum is 29.

The spelling of 21151511525 in words is "twenty-one billion, one hundred fifty-one million, five hundred eleven thousand, five hundred twenty-five".