18881557 has 2 divisors, whose sum is σ = 18881558. Its totient is φ = 18881556.

The previous prime is 18881539. The next prime is 18881567. The reversal of 18881557 is 75518881.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18714276 + 167281 = 4326^2 + 409^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18881557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18881537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9440778 + 9440779.

It is an arithmetic number, because the mean of its divisors is an integer number (9440779).

Almost surely, 2^18881557 is an apocalyptic number.

It is an amenable number.

18881557 is a deficient number, since it is larger than the sum of its proper divisors (1).

18881557 is an equidigital number, since it uses as much as digits as its factorization.

18881557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 89600, while the sum is 43.

The square root of 18881557 is about 4345.2913596214. The cubic root of 18881557 is about 266.2845288670.

The spelling of 18881557 in words is "eighteen million, eight hundred eighty-one thousand, five hundred fifty-seven".