21633491 has 4 divisors (see below), whose sum is σ = 23600184. Its totient is φ = 19666800.

The previous prime is 21633427. The next prime is 21633499. The reversal of 21633491 is 19433612.

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

It is a cyclic number.

It is not a de Polignac number, because 21633491 - 2⁶ = 21633427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21633499) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 983330 + ... + 983351.

It is an arithmetic number, because the mean of its divisors is an integer number (5900046).

Almost surely, 2^21633491 is an apocalyptic number.

21633491 is a deficient number, since it is larger than the sum of its proper divisors (1966693).

21633491 is a wasteful number, since it uses less digits than its factorization.

21633491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1966692.

The product of its digits is 3888, while the sum is 29.

The square root of 21633491 is about 4651.1816778105. The cubic root of 21633491 is about 278.6391922184.

The spelling of 21633491 in words is "twenty-one million, six hundred thirty-three thousand, four hundred ninety-one".