138640666 has 4 divisors (see below), whose sum is σ = 207961002. Its totient is φ = 69320332.

The previous prime is 138640657. The next prime is 138640669. The reversal of 138640666 is 666046831.

138640666 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 137569441 + 1071225 = 11729^2 + 1035^2 .

It is not an unprimeable number, because it can be changed into a prime (138640669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 34660165 + ... + 34660168.

Almost surely, 2^138640666 is an apocalyptic number.

138640666 is a deficient number, since it is larger than the sum of its proper divisors (69320336).

138640666 is an equidigital number, since it uses as much as digits as its factorization.

138640666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69320335.

The product of its (nonzero) digits is 124416, while the sum is 40.

The square root of 138640666 is about 11774.5771049325. The cubic root of 138640666 is about 517.5633858584.

The spelling of 138640666 in words is "one hundred thirty-eight million, six hundred forty thousand, six hundred sixty-six".