666716651 has 2 divisors, whose sum is σ = 666716652. Its totient is φ = 666716650.

The previous prime is 666716647. The next prime is 666716683. The reversal of 666716651 is 156617666.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 666716651 - 2² = 666716647 is a prime.

It is a super-2 number, since 2×666716651² = 889022185441311602, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (666716051) 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, 333358325 + 333358326.

It is an arithmetic number, because the mean of its divisors is an integer number (333358326).

Almost surely, 2^666716651 is an apocalyptic number.

666716651 is a deficient number, since it is larger than the sum of its proper divisors (1).

666716651 is an equidigital number, since it uses as much as digits as its factorization.

666716651 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 272160, while the sum is 44.

The square root of 666716651 is about 25820.8568990264. The cubic root of 666716651 is about 873.6022968592.

The spelling of 666716651 in words is "six hundred sixty-six million, seven hundred sixteen thousand, six hundred fifty-one".