640393 has 4 divisors (see below), whose sum is σ = 689668. Its totient is φ = 591120.

The previous prime is 640369. The next prime is 640411. The reversal of 640393 is 393046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 393046 = 2 ⋅196523.

It can be written as a sum of positive squares in 2 ways, for example, as 139129 + 501264 = 373^2 + 708^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640303) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24618 + ... + 24643.

It is an arithmetic number, because the mean of its divisors is an integer number (172417).

2⁶⁴⁰³⁹³ is an apocalyptic number.

It is an amenable number.

640393 is a deficient number, since it is larger than the sum of its proper divisors (49275).

640393 is a wasteful number, since it uses less digits than its factorization.

640393 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49274.

The product of its (nonzero) digits is 1944, while the sum is 25.

The square root of 640393 is about 800.2455873043. The cubic root of 640393 is about 86.1950234260.

The spelling of 640393 in words is "six hundred forty thousand, three hundred ninety-three".