21210225 has 24 divisors (see below), whose sum is σ = 35206080. Its totient is φ = 11267520.

The previous prime is 21210221. The next prime is 21210227. The reversal of 21210225 is 52201212.

It is not a de Polignac number, because 21210225 - 2² = 21210221 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21210221) 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 23 ways as a sum of consecutive naturals, for example, 28812 + ... + 29538.

It is an arithmetic number, because the mean of its divisors is an integer number (1466920).

Almost surely, 2^21210225 is an apocalyptic number.

21210225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21210225 is a deficient number, since it is larger than the sum of its proper divisors (13995855).

21210225 is a wasteful number, since it uses less digits than its factorization.

21210225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1129 (or 1124 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21210225 is about 4605.4560034811. The cubic root of 21210225 is about 276.8099892886.

Adding to 21210225 its reverse (52201212), we get a palindrome (73411437).

The spelling of 21210225 in words is "twenty-one million, two hundred ten thousand, two hundred twenty-five".