21256225 has 12 divisors (see below), whose sum is σ = 26806320. Its totient is φ = 16715600.

The previous prime is 21256153. The next prime is 21256229. The reversal of 21256225 is 52265212.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-21256225 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a self number, because there is not a number n which added to its sum of digits gives 21256225.

It is not an unprimeable number, because it can be changed into a prime (21256229) 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, 5731 + ... + 8680.

It is an arithmetic number, because the mean of its divisors is an integer number (2233860).

Almost surely, 2^21256225 is an apocalyptic number.

21256225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21256225 is a deficient number, since it is larger than the sum of its proper divisors (5550095).

21256225 is a wasteful number, since it uses less digits than its factorization.

21256225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14480 (or 14475 counting only the distinct ones).

The product of its digits is 2400, while the sum is 25.

The square root of 21256225 is about 4610.4473752555. The cubic root of 21256225 is about 277.0099567639.

The spelling of 21256225 in words is "twenty-one million, two hundred fifty-six thousand, two hundred twenty-five".