21633985 has 4 divisors (see below), whose sum is σ = 25960788. Its totient is φ = 17307184.

The previous prime is 21633973. The next prime is 21634021. The reversal of 21633985 is 58933612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3732624 + 17901361 = 1932^2 + 4231^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21633985 is a prime.

It is a Duffinian 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 3 ways as a sum of consecutive naturals, for example, 2163394 + ... + 2163403.

It is an arithmetic number, because the mean of its divisors is an integer number (6490197).

Almost surely, 2^21633985 is an apocalyptic number.

It is an amenable number.

21633985 is a deficient number, since it is larger than the sum of its proper divisors (4326803).

21633985 is an equidigital number, since it uses as much as digits as its factorization.

21633985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4326802.

The product of its digits is 38880, while the sum is 37.

The square root of 21633985 is about 4651.2347822917. The cubic root of 21633985 is about 278.6413131076.

The spelling of 21633985 in words is "twenty-one million, six hundred thirty-three thousand, nine hundred eighty-five".