21633642 has 20 divisors (see below), whose sum is σ = 48475746. Its totient is φ = 7211160.

The previous prime is 21633637. The next prime is 21633643. The reversal of 21633642 is 24633612.

21633642 is a `hidden beast` number, since 2 + 16 + 3 + 3 + 642 = 666.

It can be written as a sum of positive squares in only one way, i.e., 18740241 + 2893401 = 4329^2 + 1701^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21633643) 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 9 ways as a sum of consecutive naturals, for example, 66609 + ... + 66932.

Almost surely, 2^21633642 is an apocalyptic number.

21633642 is an abundant number, since it is smaller than the sum of its proper divisors (26842104).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21633642 is a wasteful number, since it uses less digits than its factorization.

21633642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133555 (or 133546 counting only the distinct ones).

The product of its digits is 5184, while the sum is 27.

The square root of 21633642 is about 4651.1979102162. The cubic root of 21633642 is about 278.6398405098.

The spelling of 21633642 in words is "twenty-one million, six hundred thirty-three thousand, six hundred forty-two".