21151225 has 12 divisors (see below), whose sum is σ = 26475984. Its totient is φ = 16760720.

The previous prime is 21151219. The next prime is 21151241. The reversal of 21151225 is 52215112.

It is a de Polignac number, because none of the positive numbers 2^k-21151225 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1279 + ... + 6628.

It is an arithmetic number, because the mean of its divisors is an integer number (2206332).

Almost surely, 2^21151225 is an apocalyptic number.

21151225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21151225 is a deficient number, since it is larger than the sum of its proper divisors (5324759).

21151225 is a wasteful number, since it uses less digits than its factorization.

21151225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8024 (or 8019 counting only the distinct ones).

The product of its digits is 200, while the sum is 19.

The square root of 21151225 is about 4599.0460967466. The cubic root of 21151225 is about 276.5530855850.

Adding to 21151225 its reverse (52215112), we get a palindrome (73366337).

The spelling of 21151225 in words is "twenty-one million, one hundred fifty-one thousand, two hundred twenty-five".