21818189 has 4 divisors (see below), whose sum is σ = 21858624. Its totient is φ = 21777756.

The previous prime is 21818171. The next prime is 21818201. The reversal of 21818189 is 98181812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21818189 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21818119) 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, 19397 + ... + 20490.

It is an arithmetic number, because the mean of its divisors is an integer number (5464656).

Almost surely, 2^21818189 is an apocalyptic number.

It is an amenable number.

21818189 is a deficient number, since it is larger than the sum of its proper divisors (40435).

21818189 is an equidigital number, since it uses as much as digits as its factorization.

21818189 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40434.

The product of its digits is 9216, while the sum is 38.

The square root of 21818189 is about 4670.9944337368. The cubic root of 21818189 is about 279.4299157679.

The spelling of 21818189 in words is "twenty-one million, eight hundred eighteen thousand, one hundred eighty-nine".