21872225 has 6 divisors (see below), whose sum is σ = 27121590. Its totient is φ = 17497760.

The previous prime is 21872209. The next prime is 21872231. The reversal of 21872225 is 52227812.

It can be written as a sum of positive squares in 3 ways, for example, as 1882384 + 19989841 = 1372^2 + 4471^2 .

It is not a de Polignac number, because 21872225 - 2⁴ = 21872209 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 437420 + ... + 437469.

It is an arithmetic number, because the mean of its divisors is an integer number (4520265).

Almost surely, 2^21872225 is an apocalyptic number.

21872225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21872225 is a deficient number, since it is larger than the sum of its proper divisors (5249365).

21872225 is an equidigital number, since it uses as much as digits as its factorization.

21872225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 874899 (or 874894 counting only the distinct ones).

The product of its digits is 4480, while the sum is 29.

The square root of 21872225 is about 4676.7750640799. The cubic root of 21872225 is about 279.6604088800.

The spelling of 21872225 in words is "twenty-one million, eight hundred seventy-two thousand, two hundred twenty-five".