666667 has 2 divisors, whose sum is σ = 666668. Its totient is φ = 666666.

The previous prime is 666649. The next prime is 666671. The reversal of 666667 is 766666.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 666667 - 2¹¹ = 664619 is a prime.

666667 is a lucky number.

It is a plaindrome in base 10.

It is a nialpdrome in base 7.

It is not a weakly prime, because it can be changed into another prime (666607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333333 + 333334.

It is an arithmetic number, because the mean of its divisors is an integer number (333334).

2⁶⁶⁶⁶⁶⁷ is an apocalyptic number.

666667 is a deficient number, since it is larger than the sum of its proper divisors (1).

666667 is an equidigital number, since it uses as much as digits as its factorization.

666667 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432, while the sum is 37.

The square root of 666667 is about 816.4967850518. The cubic root of 666667 is about 87.3580610333.

Subtracting 666667 from its reverse (766666), we obtain a palindrome (99999).

The spelling of 666667 in words is "six hundred sixty-six thousand, six hundred sixty-seven".