21135021525 has 24 divisors (see below), whose sum is σ = 38825818560. Its totient is φ = 11272011120.

The previous prime is 21135021511. The next prime is 21135021529. The reversal of 21135021525 is 52512053112.

21135021525 is a `hidden beast` number, since 2 + 1 + 1 + 3 + 502 + 152 + 5 = 666.

It is not a de Polignac number, because 21135021525 - 2⁵ = 21135021493 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135021529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15654897 + ... + 15656246.

It is an arithmetic number, because the mean of its divisors is an integer number (1617742440).

Almost surely, 2^21135021525 is an apocalyptic number.

21135021525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21135021525 is a deficient number, since it is larger than the sum of its proper divisors (17690797035).

21135021525 is a wasteful number, since it uses less digits than its factorization.

21135021525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31311162 (or 31311151 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 27.

Adding to 21135021525 its reverse (52512053112), we get a palindrome (73647074637).

The spelling of 21135021525 in words is "twenty-one billion, one hundred thirty-five million, twenty-one thousand, five hundred twenty-five".