21687525 has 36 divisors (see below), whose sum is σ = 39234468. Its totient is φ = 11450880.

The previous prime is 21687521. The next prime is 21687527. The reversal of 21687525 is 52578612.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 9847044 + 11840481 = 3138^2 + 3441^2 .

It is not a de Polignac number, because 21687525 - 2² = 21687521 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21687525.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21687521) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 24999 + ... + 25851.

Almost surely, 2^21687525 is an apocalyptic number.

21687525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21687525 is a deficient number, since it is larger than the sum of its proper divisors (17546943).

21687525 is a wasteful number, since it uses less digits than its factorization.

21687525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 982 (or 974 counting only the distinct ones).

The product of its digits is 33600, while the sum is 36.

The square root of 21687525 is about 4656.9866866892. The cubic root of 21687525 is about 278.8709851725.

The spelling of 21687525 in words is "twenty-one million, six hundred eighty-seven thousand, five hundred twenty-five".