18918557 has 6 divisors (see below), whose sum is σ = 22007358. Its totient is φ = 16215864.

The previous prime is 18918551. The next prime is 18918577. The reversal of 18918557 is 75581981.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 11195716 + 7722841 = 3346^2 + 2779^2 .

It is not a de Polignac number, because 18918557 - 2¹² = 18914461 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18918551) 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 5 ways as a sum of consecutive naturals, for example, 192998 + ... + 193095.

It is an arithmetic number, because the mean of its divisors is an integer number (3667893).

Almost surely, 2^18918557 is an apocalyptic number.

It is an amenable number.

18918557 is a deficient number, since it is larger than the sum of its proper divisors (3088801).

18918557 is an equidigital number, since it uses as much as digits as its factorization.

18918557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 386107 (or 386100 counting only the distinct ones).

The product of its digits is 100800, while the sum is 44.

The square root of 18918557 is about 4349.5467579967. The cubic root of 18918557 is about 266.4583510249.

The spelling of 18918557 in words is "eighteen million, nine hundred eighteen thousand, five hundred fifty-seven".