640873 has 2 divisors, whose sum is σ = 640874. Its totient is φ = 640872.

The previous prime is 640859. The next prime is 640891. The reversal of 640873 is 378046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 529984 + 110889 = 728^2 + 333^2 .

It is a cyclic number.

It is not a de Polignac number, because 640873 - 2¹⁷ = 509801 is a prime.

It is not a weakly prime, because it can be changed into another prime (640853) 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, 320436 + 320437.

It is an arithmetic number, because the mean of its divisors is an integer number (320437).

2⁶⁴⁰⁸⁷³ is an apocalyptic number.

It is an amenable number.

640873 is a deficient number, since it is larger than the sum of its proper divisors (1).

640873 is an equidigital number, since it uses as much as digits as its factorization.

640873 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 640873 is about 800.5454390601. The cubic root of 640873 is about 86.2165535793.

The spelling of 640873 in words is "six hundred forty thousand, eight hundred seventy-three".