21105525 has 36 divisors (see below), whose sum is σ = 40598592. Its totient is φ = 9646560.

The previous prime is 21105509. The next prime is 21105547. The reversal of 21105525 is 52550112.

It is not a de Polignac number, because 21105525 - 2⁴ = 21105509 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 804 + ... + 6546.

Almost surely, 2^21105525 is an apocalyptic number.

21105525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21105525 is a deficient number, since it is larger than the sum of its proper divisors (19493067).

21105525 is a wasteful number, since it uses less digits than its factorization.

21105525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5770 (or 5758 counting only the distinct ones).

The product of its (nonzero) digits is 500, while the sum is 21.

The square root of 21105525 is about 4594.0749885042. The cubic root of 21105525 is about 276.3537655407.

Adding to 21105525 its reverse (52550112), we get a palindrome (73655637).

The spelling of 21105525 in words is "twenty-one million, one hundred five thousand, five hundred twenty-five".