21818959 has 4 divisors (see below), whose sum is σ = 21861360. Its totient is φ = 21776560.

The previous prime is 21818941. The next prime is 21818963. The reversal of 21818959 is 95981812.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21818959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21818059) 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, 20419 + ... + 21460.

It is an arithmetic number, because the mean of its divisors is an integer number (5465340).

Almost surely, 2^21818959 is an apocalyptic number.

21818959 is a deficient number, since it is larger than the sum of its proper divisors (42401).

21818959 is an equidigital number, since it uses as much as digits as its factorization.

21818959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42400.

The product of its digits is 51840, while the sum is 43.

The square root of 21818959 is about 4671.0768565717. The cubic root of 21818959 is about 279.4332029106.

The spelling of 21818959 in words is "twenty-one million, eight hundred eighteen thousand, nine hundred fifty-nine".