666541987 has 2 divisors, whose sum is σ = 666541988. Its totient is φ = 666541986.

The previous prime is 666541957. The next prime is 666542033. The reversal of 666541987 is 789145666.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666541987 - 2⁷ = 666541859 is a prime.

It is not a weakly prime, because it can be changed into another prime (666541957) 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 as a sum of consecutive naturals, namely, 333270993 + 333270994.

It is an arithmetic number, because the mean of its divisors is an integer number (333270994).

Almost surely, 2^666541987 is an apocalyptic number.

666541987 is a deficient number, since it is larger than the sum of its proper divisors (1).

666541987 is an equidigital number, since it uses as much as digits as its factorization.

666541987 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2177280, while the sum is 52.

The square root of 666541987 is about 25817.4744504570. The cubic root of 666541987 is about 873.5260024804.

The spelling of 666541987 in words is "six hundred sixty-six million, five hundred forty-one thousand, nine hundred eighty-seven".