21307225 has 6 divisors (see below), whose sum is σ = 26420990. Its totient is φ = 17045760.

The previous prime is 21307193. The next prime is 21307229. The reversal of 21307225 is 52270312.

It can be written as a sum of positive squares in 3 ways, for example, as 976144 + 20331081 = 988^2 + 4509^2 .

It is not a de Polignac number, because 21307225 - 2⁵ = 21307193 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21307196 and 21307205.

It is not an unprimeable number, because it can be changed into a prime (21307229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 426120 + ... + 426169.

Almost surely, 2^21307225 is an apocalyptic number.

21307225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21307225 is a deficient number, since it is larger than the sum of its proper divisors (5113765).

21307225 is an equidigital number, since it uses as much as digits as its factorization.

21307225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 852299 (or 852294 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 22.

The square root of 21307225 is about 4615.9749782684. The cubic root of 21307225 is about 277.2313228835.

Adding to 21307225 its reverse (52270312), we get a palindrome (73577537).

The spelling of 21307225 in words is "twenty-one million, three hundred seven thousand, two hundred twenty-five".