666378191 has 8 divisors (see below), whose sum is σ = 670339824. Its totient is φ = 662428800.

The previous prime is 666378161. The next prime is 666378217. The reversal of 666378191 is 191873666.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 666378191 - 2²⁶ = 599269327 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666378161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 120401 + ... + 125813.

It is an arithmetic number, because the mean of its divisors is an integer number (83792478).

Almost surely, 2^666378191 is an apocalyptic number.

666378191 is a deficient number, since it is larger than the sum of its proper divisors (3961633).

666378191 is a wasteful number, since it uses less digits than its factorization.

666378191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6121.

The product of its digits is 326592, while the sum is 47.

The square root of 666378191 is about 25814.3020630038. The cubic root of 666378191 is about 873.4544432040.

The spelling of 666378191 in words is "six hundred sixty-six million, three hundred seventy-eight thousand, one hundred ninety-one".