640663 has 2 divisors, whose sum is σ = 640664. Its totient is φ = 640662.

The previous prime is 640649. The next prime is 640667. The reversal of 640663 is 366046.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640663 - 2⁵ = 640631 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320331 + 320332.

It is an arithmetic number, because the mean of its divisors is an integer number (320332).

2⁶⁴⁰⁶⁶³ is an apocalyptic number.

640663 is a deficient number, since it is larger than the sum of its proper divisors (1).

640663 is an equidigital number, since it uses as much as digits as its factorization.

640663 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 25.

The square root of 640663 is about 800.4142677389. The cubic root of 640663 is about 86.2071354605.

The spelling of 640663 in words is "six hundred forty thousand, six hundred sixty-three".