21538525 has 6 divisors (see below), whose sum is σ = 26707802. Its totient is φ = 17230800.

The previous prime is 21538523. The next prime is 21538547. The reversal of 21538525 is 52583512.

It can be written as a sum of positive squares in 3 ways, for example, as 2893401 + 18645124 = 1701^2 + 4318^2 .

It is not a de Polignac number, because 21538525 - 2¹ = 21538523 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 430746 + ... + 430795.

Almost surely, 2^21538525 is an apocalyptic number.

21538525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21538525 is a deficient number, since it is larger than the sum of its proper divisors (5169277).

21538525 is an equidigital number, since it uses as much as digits as its factorization.

21538525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 861551 (or 861546 counting only the distinct ones).

The product of its digits is 12000, while the sum is 31.

The square root of 21538525 is about 4640.9616460385. The cubic root of 21538525 is about 278.2308737180.

The spelling of 21538525 in words is "twenty-one million, five hundred thirty-eight thousand, five hundred twenty-five".