21531825 has 120 divisors (see below), whose sum is σ = 48012800. Its totient is φ = 9525600.

The previous prime is 21531821. The next prime is 21531827. The reversal of 21531825 is 52813512.

It is a happy number.

It is not a de Polignac number, because 21531825 - 2² = 21531821 is a prime.

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21531821) by changing a digit.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 694560 + ... + 694590.

Almost surely, 2^21531825 is an apocalyptic number.

21531825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21531825 is an abundant number, since it is smaller than the sum of its proper divisors (26480975).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21531825 is an equidigital number, since it uses as much as digits as its factorization.

21531825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74 (or 46 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 21531825 is about 4640.2397567367. The cubic root of 21531825 is about 278.2020209193.

The spelling of 21531825 in words is "twenty-one million, five hundred thirty-one thousand, eight hundred twenty-five".