666643 has 2 divisors, whose sum is σ = 666644. Its totient is φ = 666642.

The previous prime is 666637. The next prime is 666647. The reversal of 666643 is 346666.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 666643 - 2¹⁷ = 535571 is a prime.

It is a nialpdrome in base 10.

It is not a weakly prime, because it can be changed into another prime (666647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333321 + 333322.

It is an arithmetic number, because the mean of its divisors is an integer number (333322).

2⁶⁶⁶⁶⁴³ is an apocalyptic number.

666643 is a deficient number, since it is larger than the sum of its proper divisors (1).

666643 is an equidigital number, since it uses as much as digits as its factorization.

666643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 31.

The square root of 666643 is about 816.4820879848. The cubic root of 666643 is about 87.3570127245.

The spelling of 666643 in words is "six hundred sixty-six thousand, six hundred forty-three".