666671891 has 2 divisors, whose sum is σ = 666671892. Its totient is φ = 666671890.

The previous prime is 666671879. The next prime is 666671903. The reversal of 666671891 is 198176666.

It is a balanced prime because it is at equal distance from previous prime (666671879) and next prime (666671903).

It is a cyclic number.

It is not a de Polignac number, because 666671891 - 2⁶ = 666671827 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (666671851) 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, 333335945 + 333335946.

It is an arithmetic number, because the mean of its divisors is an integer number (333335946).

Almost surely, 2^666671891 is an apocalyptic number.

666671891 is a deficient number, since it is larger than the sum of its proper divisors (1).

666671891 is an equidigital number, since it uses as much as digits as its factorization.

666671891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 653184, while the sum is 50.

The square root of 666671891 is about 25819.9901432979. The cubic root of 666671891 is about 873.5827466681.

The spelling of 666671891 in words is "six hundred sixty-six million, six hundred seventy-one thousand, eight hundred ninety-one".