21285225 has 72 divisors (see below), whose sum is σ = 43330560. Its totient is φ = 9901440.

The previous prime is 21285223. The next prime is 21285233. The reversal of 21285225 is 52258212.

It is not a de Polignac number, because 21285225 - 2¹ = 21285223 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21285223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 55384 + ... + 55766.

Almost surely, 2^21285225 is an apocalyptic number.

21285225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21285225 is an abundant number, since it is smaller than the sum of its proper divisors (22045335).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21285225 is a wasteful number, since it uses less digits than its factorization.

21285225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 431 (or 423 counting only the distinct ones).

The product of its digits is 3200, while the sum is 27.

The square root of 21285225 is about 4613.5913343078. The cubic root of 21285225 is about 277.1358749867.

The spelling of 21285225 in words is "twenty-one million, two hundred eighty-five thousand, two hundred twenty-five".