18311989 has 4 divisors (see below), whose sum is σ = 18474156. Its totient is φ = 18149824.

The previous prime is 18311987. The next prime is 18312013. The reversal of 18311989 is 98911381.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 98911381 = 1601 ⋅61781.

It can be written as a sum of positive squares in 2 ways, for example, as 4695889 + 13616100 = 2167^2 + 3690^2 .

It is a cyclic number.

It is not a de Polignac number, because 18311989 - 2¹ = 18311987 is a prime.

It is a super-2 number, since 2×18311989² = 670657882272242, 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 (18311983) 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, 80914 + ... + 81139.

It is an arithmetic number, because the mean of its divisors is an integer number (4618539).

Almost surely, 2^18311989 is an apocalyptic number.

It is an amenable number.

18311989 is a deficient number, since it is larger than the sum of its proper divisors (162167).

18311989 is a wasteful number, since it uses less digits than its factorization.

18311989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162166.

The product of its digits is 15552, while the sum is 40.

The square root of 18311989 is about 4279.2509858619. The cubic root of 18311989 is about 263.5796273217.

The spelling of 18311989 in words is "eighteen million, three hundred eleven thousand, nine hundred eighty-nine".