21810225 has 12 divisors (see below), whose sum is σ = 36059696. Its totient is φ = 11632080.

The previous prime is 21810221. The next prime is 21810253. The reversal of 21810225 is 52201812.

It is a happy number.

It is not a de Polignac number, because 21810225 - 2² = 21810221 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21810221) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 145327 + ... + 145476.

Almost surely, 2^21810225 is an apocalyptic number.

21810225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21810225 is a deficient number, since it is larger than the sum of its proper divisors (14249471).

21810225 is a wasteful number, since it uses less digits than its factorization.

21810225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290816 (or 290811 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 21.

The square root of 21810225 is about 4670.1418608004. The cubic root of 21810225 is about 279.3959127827.

The spelling of 21810225 in words is "twenty-one million, eight hundred ten thousand, two hundred twenty-five".