640973 has 2 divisors, whose sum is σ = 640974. Its totient is φ = 640972.

The previous prime is 640967. The next prime is 640993. The reversal of 640973 is 379046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 537289 + 103684 = 733^2 + 322^2 .

It is a cyclic number.

It is not a de Polignac number, because 640973 - 2⁴ = 640957 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 polite number, since it can be written as a sum of consecutive naturals, namely, 320486 + 320487.

It is an arithmetic number, because the mean of its divisors is an integer number (320487).

2⁶⁴⁰⁹⁷³ is an apocalyptic number.

It is an amenable number.

640973 is a deficient number, since it is larger than the sum of its proper divisors (1).

640973 is an equidigital number, since it uses as much as digits as its factorization.

640973 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 29.

The square root of 640973 is about 800.6078940405. The cubic root of 640973 is about 86.2210376747.

It can be divided in two parts, 64097 and 3, that multiplied together give a palindrome (192291).

The spelling of 640973 in words is "six hundred forty thousand, nine hundred seventy-three".