21315225 has 24 divisors (see below), whose sum is σ = 35845920. Its totient is φ = 11173120.

The previous prime is 21315223. The next prime is 21315241. The reversal of 21315225 is 52251312.

It is not a de Polignac number, because 21315225 - 2¹ = 21315223 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21315221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2017 + ... + 6833.

It is an arithmetic number, because the mean of its divisors is an integer number (1493580).

Almost surely, 2^21315225 is an apocalyptic number.

21315225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21315225 is a deficient number, since it is larger than the sum of its proper divisors (14530695).

21315225 is a wasteful number, since it uses less digits than its factorization.

21315225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4889 (or 4884 counting only the distinct ones).

The product of its digits is 600, while the sum is 21.

The square root of 21315225 is about 4616.8414527683. The cubic root of 21315225 is about 277.2660149198.

Adding to 21315225 its reverse (52251312), we get a palindrome (73566537).

The spelling of 21315225 in words is "twenty-one million, three hundred fifteen thousand, two hundred twenty-five".