18155986 has 4 divisors (see below), whose sum is σ = 27233982. Its totient is φ = 9077992.

The previous prime is 18155981. The next prime is 18156013. The reversal of 18155986 is 68955181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 68955181 = 263 ⋅262187.

It can be written as a sum of positive squares in only one way, i.e., 10118761 + 8037225 = 3181^2 + 2835^2 .

It is not an unprimeable number, because it can be changed into a prime (18155981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4538995 + ... + 4538998.

Almost surely, 2^18155986 is an apocalyptic number.

18155986 is a deficient number, since it is larger than the sum of its proper divisors (9077996).

18155986 is an equidigital number, since it uses as much as digits as its factorization.

18155986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9077995.

The product of its digits is 86400, while the sum is 43.

The square root of 18155986 is about 4260.9841586188. The cubic root of 18155986 is about 262.8289982187.

The spelling of 18155986 in words is "eighteen million, one hundred fifty-five thousand, nine hundred eighty-six".