21042225 has 36 divisors (see below), whose sum is σ = 38625132. Its totient is φ = 10944000.

The previous prime is 21042223. The next prime is 21042251. The reversal of 21042225 is 52224012.

It can be written as a sum of positive squares in 6 ways, for example, as 2792241 + 18249984 = 1671^2 + 4272^2 .

It is not a de Polignac number, because 21042225 - 2¹ = 21042223 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21042198 and 21042207.

It is not an unprimeable number, because it can be changed into a prime (21042223) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 8085 + ... + 10365.

Almost surely, 2^21042225 is an apocalyptic number.

21042225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21042225 is a deficient number, since it is larger than the sum of its proper divisors (17582907).

21042225 is a wasteful number, since it uses less digits than its factorization.

21042225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2338 (or 2330 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21042225 is about 4587.1805065857. The cubic root of 21042225 is about 276.0772074487.

Adding to 21042225 its reverse (52224012), we get a palindrome (73266237).

The spelling of 21042225 in words is "twenty-one million, forty-two thousand, two hundred twenty-five".