21630405 has 32 divisors (see below), whose sum is σ = 36062208. Its totient is φ = 11059200.

The previous prime is 21630391. The next prime is 21630421. The reversal of 21630405 is 50403612.

It is a happy number.

It is not a de Polignac number, because 21630405 - 2⁷ = 21630277 is a prime.

It is a congruent number.

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 31 ways as a sum of consecutive naturals, for example, 84037 + ... + 84293.

It is an arithmetic number, because the mean of its divisors is an integer number (1126944).

Almost surely, 2^21630405 is an apocalyptic number.

It is an amenable number.

21630405 is a deficient number, since it is larger than the sum of its proper divisors (14431803).

21630405 is a wasteful number, since it uses less digits than its factorization.

21630405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 477.

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

The square root of 21630405 is about 4650.8499223260. The cubic root of 21630405 is about 278.6259423699.

The spelling of 21630405 in words is "twenty-one million, six hundred thirty thousand, four hundred five".