18551989 has 2 divisors, whose sum is σ = 18551990. Its totient is φ = 18551988.

The previous prime is 18551971. The next prime is 18551993. The reversal of 18551989 is 98915581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17363889 + 1188100 = 4167^2 + 1090^2 .

It is a cyclic number.

It is not a de Polignac number, because 18551989 - 2⁷ = 18551861 is a prime.

It is a super-2 number, since 2×18551989² = 688352591712242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18551959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9275994 + 9275995.

It is an arithmetic number, because the mean of its divisors is an integer number (9275995).

Almost surely, 2^18551989 is an apocalyptic number.

It is an amenable number.

18551989 is a deficient number, since it is larger than the sum of its proper divisors (1).

18551989 is an equidigital number, since it uses as much as digits as its factorization.

18551989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 129600, while the sum is 46.

The square root of 18551989 is about 4307.2019920129. The cubic root of 18551989 is about 264.7261392941.

It can be divided in two parts, 1855 and 1989, that added together give a square (3844 = 62²).

The spelling of 18551989 in words is "eighteen million, five hundred fifty-one thousand, nine hundred eighty-nine".