666242991 has 12 divisors (see below), whose sum is σ = 962699920. Its totient is φ = 444000960.

The previous prime is 666242987. The next prime is 666243029. The reversal of 666242991 is 199242666.

It is not a de Polignac number, because 666242991 - 2² = 666242987 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 (666242981) 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 11 ways as a sum of consecutive naturals, for example, 16230 + ... + 39948.

Almost surely, 2^666242991 is an apocalyptic number.

666242991 is a deficient number, since it is larger than the sum of its proper divisors (296456929).

666242991 is a wasteful number, since it uses less digits than its factorization.

666242991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26846 (or 26843 counting only the distinct ones).

The product of its digits is 279936, while the sum is 45.

The square root of 666242991 is about 25811.6832267871. The cubic root of 666242991 is about 873.3953681274.

The spelling of 666242991 in words is "six hundred sixty-six million, two hundred forty-two thousand, nine hundred ninety-one".