640385 has 8 divisors (see below), whose sum is σ = 773376. Its totient is φ = 509040.

The previous prime is 640369. The next prime is 640411. The reversal of 640385 is 583046.

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

It is not a de Polignac number, because 640385 - 2⁴ = 640369 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640385.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 752 + ... + 1358.

It is an arithmetic number, because the mean of its divisors is an integer number (96672).

2⁶⁴⁰³⁸⁵ is an apocalyptic number.

It is an amenable number.

640385 is a deficient number, since it is larger than the sum of its proper divisors (132991).

640385 is a wasteful number, since it uses less digits than its factorization.

640385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 823.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 640385 is about 800.2405888231. The cubic root of 640385 is about 86.1946644989.

The spelling of 640385 in words is "six hundred forty thousand, three hundred eighty-five".