21351225 has 48 divisors (see below), whose sum is σ = 41013248. Its totient is φ = 9599040.

The previous prime is 21351217. The next prime is 21351227. The reversal of 21351225 is 52215312.

It is not a de Polignac number, because 21351225 - 2³ = 21351217 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21351227) 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 47 ways as a sum of consecutive naturals, for example, 34872 + ... + 35478.

Almost surely, 2^21351225 is an apocalyptic number.

21351225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21351225 is a deficient number, since it is larger than the sum of its proper divisors (19662023).

21351225 is a wasteful number, since it uses less digits than its factorization.

21351225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 694 (or 689 counting only the distinct ones).

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

The square root of 21351225 is about 4620.7385773272. The cubic root of 21351225 is about 277.4220217552.

Adding to 21351225 its reverse (52215312), we get a palindrome (73566537).

The spelling of 21351225 in words is "twenty-one million, three hundred fifty-one thousand, two hundred twenty-five".