21018189 has 4 divisors (see below), whose sum is σ = 28024256. Its totient is φ = 14012124.

The previous prime is 21018167. The next prime is 21018191. The reversal of 21018189 is 98181012.

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 not a de Polignac number, because 21018189 - 2⁹ = 21017677 is a prime.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018149) 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 3 ways as a sum of consecutive naturals, for example, 3503029 + ... + 3503034.

It is an arithmetic number, because the mean of its divisors is an integer number (7006064).

Almost surely, 2^21018189 is an apocalyptic number.

It is an amenable number.

21018189 is a deficient number, since it is larger than the sum of its proper divisors (7006067).

21018189 is an equidigital number, since it uses as much as digits as its factorization.

21018189 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7006066.

The product of its (nonzero) digits is 1152, while the sum is 30.

The square root of 21018189 is about 4584.5598480116. The cubic root of 21018189 is about 275.9720487342.

The spelling of 21018189 in words is "twenty-one million, eighteen thousand, one hundred eighty-nine".