21630225 has 12 divisors (see below), whose sum is σ = 35762096. Its totient is φ = 11536080.

The previous prime is 21630223. The next prime is 21630229. The reversal of 21630225 is 52203612.

It is not a de Polignac number, because 21630225 - 2¹ = 21630223 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21630223) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 144127 + ... + 144276.

Almost surely, 2^21630225 is an apocalyptic number.

21630225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21630225 is a deficient number, since it is larger than the sum of its proper divisors (14131871).

21630225 is a wasteful number, since it uses less digits than its factorization.

21630225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 288416 (or 288411 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21630225 is about 4650.8305709841. The cubic root of 21630225 is about 278.6251694947.

Adding to 21630225 its reverse (52203612), we get a palindrome (73833837).

The spelling of 21630225 in words is "twenty-one million, six hundred thirty thousand, two hundred twenty-five".