21621625 has 8 divisors (see below), whose sum is σ = 26983944. Its totient is φ = 17297200.

The previous prime is 21621577. The next prime is 21621629. The reversal of 21621625 is 52612612.

It can be written as a sum of positive squares in 4 ways, for example, as 4999696 + 16621929 = 2236^2 + 4077^2 .

It is not a de Polignac number, because 21621625 - 2⁷ = 21621497 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21621625.

It is not an unprimeable number, because it can be changed into a prime (21621629) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 86362 + ... + 86611.

It is an arithmetic number, because the mean of its divisors is an integer number (3372993).

Almost surely, 2^21621625 is an apocalyptic number.

21621625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21621625 is a deficient number, since it is larger than the sum of its proper divisors (5362319).

21621625 is an equidigital number, since it uses as much as digits as its factorization.

21621625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172988 (or 172978 counting only the distinct ones).

The product of its digits is 1440, while the sum is 25.

The square root of 21621625 is about 4649.9059130266. The cubic root of 21621625 is about 278.5882382393.

The spelling of 21621625 in words is "twenty-one million, six hundred twenty-one thousand, six hundred twenty-five".