21245225 has 12 divisors (see below), whose sum is σ = 26958096. Its totient is φ = 16600080.

The previous prime is 21245221. The next prime is 21245227. The reversal of 21245225 is 52254212.

It is not a de Polignac number, because 21245225 - 2² = 21245221 is a prime.

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 21245225.

It is not an unprimeable number, because it can be changed into a prime (21245221) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8807 + ... + 10956.

It is an arithmetic number, because the mean of its divisors is an integer number (2246508).

Almost surely, 2^21245225 is an apocalyptic number.

21245225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21245225 is a deficient number, since it is larger than the sum of its proper divisors (5712871).

21245225 is a wasteful number, since it uses less digits than its factorization.

21245225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19816 (or 19811 counting only the distinct ones).

The product of its digits is 1600, while the sum is 23.

The square root of 21245225 is about 4609.2542780801. The cubic root of 21245225 is about 276.9621647203.

Adding to 21245225 its reverse (52254212), we get a palindrome (73499437).

The spelling of 21245225 in words is "twenty-one million, two hundred forty-five thousand, two hundred twenty-five".