21124225 has 24 divisors (see below), whose sum is σ = 27607608. Its totient is φ = 16012800.

The previous prime is 21124199. The next prime is 21124253. The reversal of 21124225 is 52242112.

It can be written as a sum of positive squares in 12 ways, for example, as 11532816 + 9591409 = 3396^2 + 3097^2 .

It is not a de Polignac number, because 21124225 - 2²³ = 12735617 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 37647 + ... + 38203.

It is an arithmetic number, because the mean of its divisors is an integer number (1150317).

Almost surely, 2^21124225 is an apocalyptic number.

21124225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21124225 is a deficient number, since it is larger than the sum of its proper divisors (6483383).

21124225 is a wasteful number, since it uses less digits than its factorization.

21124225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645 (or 640 counting only the distinct ones).

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

The square root of 21124225 is about 4596.1097680538. The cubic root of 21124225 is about 276.4353601294.

Adding to 21124225 its reverse (52242112), we get a palindrome (73366337).

It can be divided in two parts, 2112 and 4225, that multiplied together give a triangular number (8923200 = T₄₂₂₄).

The spelling of 21124225 in words is "twenty-one million, one hundred twenty-four thousand, two hundred twenty-five".