18581989 has 4 divisors (see below), whose sum is σ = 19181440. Its totient is φ = 17982540.

The previous prime is 18581971. The next prime is 18582001. The reversal of 18581989 is 98918581.

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, and also an emirpimes, since its reverse is a distinct semiprime: 98918581 = 421 ⋅234961.

It is a cyclic number.

It is not a de Polignac number, because 18581989 - 2⁹ = 18581477 is a prime.

It is a super-2 number, since 2×18581989² = 690580630392242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18581389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 299679 + ... + 299740.

It is an arithmetic number, because the mean of its divisors is an integer number (4795360).

Almost surely, 2^18581989 is an apocalyptic number.

It is an amenable number.

18581989 is a deficient number, since it is larger than the sum of its proper divisors (599451).

18581989 is an equidigital number, since it uses as much as digits as its factorization.

18581989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 599450.

The product of its digits is 207360, while the sum is 49.

The square root of 18581989 is about 4310.6831245175. The cubic root of 18581989 is about 264.8687566561.

The spelling of 18581989 in words is "eighteen million, five hundred eighty-one thousand, nine hundred eighty-nine".