640398 has 32 divisors (see below), whose sum is σ = 1446912. Its totient is φ = 187200.

The previous prime is 640369. The next prime is 640411. The reversal of 640398 is 893046.

640398 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an Ulam number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640398.

It is an unprimeable number.

640398 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1890 + ... + 2202.

It is an arithmetic number, because the mean of its divisors is an integer number (45216).

2⁶⁴⁰³⁹⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640398, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (723456).

640398 is an abundant number, since it is smaller than the sum of its proper divisors (806514).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640398 is a wasteful number, since it uses less digits than its factorization.

640398 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 360.

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 640398 is about 800.2487113392. The cubic root of 640398 is about 86.1952477538.

It can be divided in two parts, 6 and 40398, that added together give a palindrome (40404).

The spelling of 640398 in words is "six hundred forty thousand, three hundred ninety-eight".