640394 has 8 divisors (see below), whose sum is σ = 970788. Its totient is φ = 316800.

The previous prime is 640369. The next prime is 640411. The reversal of 640394 is 493046.

It can be written as a sum of positive squares in 2 ways, for example, as 619369 + 21025 = 787^2 + 145^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640394.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1457 + ... + 1844.

2⁶⁴⁰³⁹⁴ is an apocalyptic number.

640394 is a deficient number, since it is larger than the sum of its proper divisors (330394).

640394 is a wasteful number, since it uses less digits than its factorization.

640394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3400.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 640394 is about 800.2462121122. The cubic root of 640394 is about 86.1950682916.

The spelling of 640394 in words is "six hundred forty thousand, three hundred ninety-four".