21643625 has 8 divisors (see below), whose sum is σ = 27011400. Its totient is φ = 17314800.

The previous prime is 21643607. The next prime is 21643691. The reversal of 21643625 is 52634612.

It can be written as a sum of positive squares in 4 ways, for example, as 1104601 + 20539024 = 1051^2 + 4532^2 .

It is not a de Polignac number, because 21643625 - 2¹⁰ = 21642601 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 86450 + ... + 86699.

It is an arithmetic number, because the mean of its divisors is an integer number (3376425).

Almost surely, 2^21643625 is an apocalyptic number.

21643625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21643625 is a deficient number, since it is larger than the sum of its proper divisors (5367775).

21643625 is an equidigital number, since it uses as much as digits as its factorization.

21643625 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173164 (or 173154 counting only the distinct ones).

The product of its digits is 8640, while the sum is 29.

The square root of 21643625 is about 4652.2709508368. The cubic root of 21643625 is about 278.6826940396.

The spelling of 21643625 in words is "twenty-one million, six hundred forty-three thousand, six hundred twenty-five".