666647 has 2 divisors, whose sum is σ = 666648. Its totient is φ = 666646.

The previous prime is 666643. The next prime is 666649. The reversal of 666647 is 746666.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 666647 - 2² = 666643 is a prime.

Together with 666649, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333323 + 333324.

It is an arithmetic number, because the mean of its divisors is an integer number (333324).

2⁶⁶⁶⁶⁴⁷ is an apocalyptic number.

666647 is a deficient number, since it is larger than the sum of its proper divisors (1).

666647 is an equidigital number, since it uses as much as digits as its factorization.

666647 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 35.

The square root of 666647 is about 816.4845375143. The cubic root of 666647 is about 87.3571874444.

The spelling of 666647 in words is "six hundred sixty-six thousand, six hundred forty-seven".