21803009 has 4 divisors (see below), whose sum is σ = 21877716. Its totient is φ = 21728304.

The previous prime is 21803003. The next prime is 21803039. The reversal of 21803009 is 90030812.

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 16785409 + 5017600 = 4097^2 + 2240^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21803009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21803003) 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, 36914 + ... + 37499.

It is an arithmetic number, because the mean of its divisors is an integer number (5469429).

Almost surely, 2^21803009 is an apocalyptic number.

It is an amenable number.

21803009 is a deficient number, since it is larger than the sum of its proper divisors (74707).

21803009 is an equidigital number, since it uses as much as digits as its factorization.

21803009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74706.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 21803009 is about 4669.3692293499. The cubic root of 21803009 is about 279.3650962996.

The spelling of 21803009 in words is "twenty-one million, eight hundred three thousand, nine".