640993 has 2 divisors, whose sum is σ = 640994. Its totient is φ = 640992.

The previous prime is 640973. The next prime is 641051. The reversal of 640993 is 399046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 567009 + 73984 = 753^2 + 272^2 .

It is a cyclic number.

It is not a de Polignac number, because 640993 - 2¹⁷ = 509921 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640933) 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, 320496 + 320497.

It is an arithmetic number, because the mean of its divisors is an integer number (320497).

2⁶⁴⁰⁹⁹³ is an apocalyptic number.

It is an amenable number.

640993 is a deficient number, since it is larger than the sum of its proper divisors (1).

640993 is an equidigital number, since it uses as much as digits as its factorization.

640993 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5832, while the sum is 31.

The square root of 640993 is about 800.6203844520. The cubic root of 640993 is about 86.2219344378.

The spelling of 640993 in words is "six hundred forty thousand, nine hundred ninety-three".