21712225 has 6 divisors (see below), whose sum is σ = 26923190. Its totient is φ = 17369760.

The previous prime is 21712211. The next prime is 21712237. The reversal of 21712225 is 52221712.

It can be written as a sum of positive squares in 3 ways, for example, as 2211169 + 19501056 = 1487^2 + 4416^2 .

It is not a de Polignac number, because 21712225 - 2⁹ = 21711713 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21712196 and 21712205.

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, 434220 + ... + 434269.

Almost surely, 2^21712225 is an apocalyptic number.

21712225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21712225 is a deficient number, since it is larger than the sum of its proper divisors (5210965).

21712225 is an equidigital number, since it uses as much as digits as its factorization.

21712225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 868499 (or 868494 counting only the distinct ones).

The product of its digits is 560, while the sum is 22.

The square root of 21712225 is about 4659.6378614652. The cubic root of 21712225 is about 278.9768140614.

Adding to 21712225 its reverse (52221712), we get a palindrome (73933937).

The spelling of 21712225 in words is "twenty-one million, seven hundred twelve thousand, two hundred twenty-five".