18401989 has 4 divisors (see below), whose sum is σ = 18850860. Its totient is φ = 17953120.

The previous prime is 18401983. The next prime is 18402011. The reversal of 18401989 is 98910481.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 98910481 = 283 ⋅349507.

It can be written as a sum of positive squares in 2 ways, for example, as 3771364 + 14630625 = 1942^2 + 3825^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18401989 is a prime.

It is a super-2 number, since 2×18401989² = 677266398312242, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18401983) 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, 224374 + ... + 224455.

It is an arithmetic number, because the mean of its divisors is an integer number (4712715).

Almost surely, 2^18401989 is an apocalyptic number.

It is an amenable number.

18401989 is a deficient number, since it is larger than the sum of its proper divisors (448871).

18401989 is an equidigital number, since it uses as much as digits as its factorization.

18401989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 448870.

The product of its (nonzero) digits is 20736, while the sum is 40.

The square root of 18401989 is about 4289.7539556483. The cubic root of 18401989 is about 264.0107366692.

The spelling of 18401989 in words is "eighteen million, four hundred one thousand, nine hundred eighty-nine".