666944191 has 4 divisors (see below), whose sum is σ = 667111000. Its totient is φ = 666777384.

The previous prime is 666944189. The next prime is 666944207. The reversal of 666944191 is 191449666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 191449666 = 2 ⋅95724833.

It is a cyclic number.

It is not a de Polignac number, because 666944191 - 2¹ = 666944189 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 (666944111) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 77256 + ... + 85453.

It is an arithmetic number, because the mean of its divisors is an integer number (166777750).

Almost surely, 2^666944191 is an apocalyptic number.

666944191 is a deficient number, since it is larger than the sum of its proper divisors (166809).

666944191 is a wasteful number, since it uses less digits than its factorization.

666944191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166808.

The product of its digits is 279936, while the sum is 46.

The square root of 666944191 is about 25825.2626511329. The cubic root of 666944191 is about 873.7016678375.

The spelling of 666944191 in words is "six hundred sixty-six million, nine hundred forty-four thousand, one hundred ninety-one".