21421225 has 24 divisors (see below), whose sum is σ = 30662720. Its totient is φ = 14541120.

The previous prime is 21421201. The next prime is 21421243. The reversal of 21421225 is 52212412.

It is not a de Polignac number, because 21421225 - 2⁷ = 21421097 is a prime.

It is a congruent number.

It is an unprimeable number.

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, 18514 + ... + 19636.

Almost surely, 2^21421225 is an apocalyptic number.

21421225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21421225 is a deficient number, since it is larger than the sum of its proper divisors (9241495).

21421225 is a wasteful number, since it uses less digits than its factorization.

21421225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1249 (or 1244 counting only the distinct ones).

The product of its digits is 320, while the sum is 19.

The square root of 21421225 is about 4628.3069258639. The cubic root of 21421225 is about 277.7248671075.

Adding to 21421225 its reverse (52212412), we get a palindrome (73633637).

The spelling of 21421225 in words is "twenty-one million, four hundred twenty-one thousand, two hundred twenty-five".