640399 has 8 divisors (see below), whose sum is σ = 670032. Its totient is φ = 611520.

The previous prime is 640369. The next prime is 640411. The reversal of 640399 is 993046.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640399 is a prime.

It is a super-2 number, since 2×640399² = 820221758402, which contains 22 as substring.

It is a Duffinian number.

640399 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 640399.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640369) 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 in 7 ways as a sum of consecutive naturals, for example, 2139 + ... + 2419.

It is an arithmetic number, because the mean of its divisors is an integer number (83754).

2⁶⁴⁰³⁹⁹ is an apocalyptic number.

640399 is a deficient number, since it is larger than the sum of its proper divisors (29633).

640399 is a wasteful number, since it uses less digits than its factorization.

640399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 377.

The product of its (nonzero) digits is 5832, while the sum is 31.

The square root of 640399 is about 800.2493361447. The cubic root of 640399 is about 86.1952926193.

The spelling of 640399 in words is "six hundred forty thousand, three hundred ninety-nine".