21404225 has 6 divisors (see below), whose sum is σ = 26541270. Its totient is φ = 17123360.

The previous prime is 21404213. The next prime is 21404263. The reversal of 21404225 is 52240412.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 179776 + 21224449 = 424^2 + 4607^2 .

It is not a de Polignac number, because 21404225 - 2¹⁴ = 21387841 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21404197 and 21404206.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 428060 + ... + 428109.

It is an arithmetic number, because the mean of its divisors is an integer number (4423545).

Almost surely, 2^21404225 is an apocalyptic number.

21404225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21404225 is a deficient number, since it is larger than the sum of its proper divisors (5137045).

21404225 is an equidigital number, since it uses as much as digits as its factorization.

21404225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 856179 (or 856174 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21404225 is about 4626.4700366478. The cubic root of 21404225 is about 277.6513796786.

Adding to 21404225 its reverse (52240412), we get a palindrome (73644637).

The spelling of 21404225 in words is "twenty-one million, four hundred four thousand, two hundred twenty-five".