21261225 has 24 divisors (see below), whose sum is σ = 35354880. Its totient is φ = 11273920.

The previous prime is 21261217. The next prime is 21261239. The reversal of 21261225 is 52216212.

It is a happy number.

It is not a de Polignac number, because 21261225 - 2³ = 21261217 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14056 + ... + 15494.

It is an arithmetic number, because the mean of its divisors is an integer number (1473120).

Almost surely, 2^21261225 is an apocalyptic number.

21261225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21261225 is a deficient number, since it is larger than the sum of its proper divisors (14093655).

21261225 is a wasteful number, since it uses less digits than its factorization.

21261225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1649 (or 1644 counting only the distinct ones).

The product of its digits is 480, while the sum is 21.

The square root of 21261225 is about 4610.9895900989. The cubic root of 21261225 is about 277.0316749696.

Adding to 21261225 its reverse (52216212), we get a palindrome (73477437).

The spelling of 21261225 in words is "twenty-one million, two hundred sixty-one thousand, two hundred twenty-five".