66139618 has 4 divisors (see below), whose sum is σ = 99209430. Its totient is φ = 33069808.

The previous prime is 66139597. The next prime is 66139621. The reversal of 66139618 is 81693166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 81693166 = 2 ⋅40846583.

It can be written as a sum of positive squares in only one way, i.e., 65173329 + 966289 = 8073^2 + 983^2 .

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 an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 16534903 + ... + 16534906.

Almost surely, 2^66139618 is an apocalyptic number.

66139618 is a deficient number, since it is larger than the sum of its proper divisors (33069812).

66139618 is a wasteful number, since it uses less digits than its factorization.

66139618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33069811.

The product of its digits is 46656, while the sum is 40.

The square root of 66139618 is about 8132.6267589260. The cubic root of 66139618 is about 404.4087659280.

The spelling of 66139618 in words is "sixty-six million, one hundred thirty-nine thousand, six hundred eighteen".