166642666 has 4 divisors (see below), whose sum is σ = 249964002. Its totient is φ = 83321332.

The previous prime is 166642661. The next prime is 166642691. The reversal of 166642666 is 666246661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 666246661 = 3677 ⋅181193.

It can be written as a sum of positive squares in only one way, i.e., 143400625 + 23242041 = 11975^2 + 4821^2 .

It is not an unprimeable number, because it can be changed into a prime (166642661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41660665 + ... + 41660668.

Almost surely, 2^166642666 is an apocalyptic number.

166642666 is a deficient number, since it is larger than the sum of its proper divisors (83321336).

166642666 is an equidigital number, since it uses as much as digits as its factorization.

166642666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83321335.

The product of its digits is 373248, while the sum is 43.

The square root of 166642666 is about 12909.0149120682. The cubic root of 166642666 is about 550.2947907292.

The spelling of 166642666 in words is "one hundred sixty-six million, six hundred forty-two thousand, six hundred sixty-six".