21390225 has 24 divisors (see below), whose sum is σ = 35518560. Its totient is φ = 11358720.

The previous prime is 21390163. The next prime is 21390247. The reversal of 21390225 is 52209312.

It is not a de Polignac number, because 21390225 - 2⁹ = 21389713 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21390195 and 21390204.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 22561 + ... + 23489.

It is an arithmetic number, because the mean of its divisors is an integer number (1479940).

Almost surely, 2^21390225 is an apocalyptic number.

21390225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21390225 is a deficient number, since it is larger than the sum of its proper divisors (14128335).

21390225 is a wasteful number, since it uses less digits than its factorization.

21390225 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 (nonzero) digits is 1080, while the sum is 24.

The square root of 21390225 is about 4624.9567565546. The cubic root of 21390225 is about 277.5908313972.

Adding to 21390225 its reverse (52209312), we get a palindrome (73599537).

The spelling of 21390225 in words is "twenty-one million, three hundred ninety thousand, two hundred twenty-five".