640842 has 24 divisors (see below), whose sum is σ = 1337856. Its totient is φ = 204624.

The previous prime is 640837. The next prime is 640847. The reversal of 640842 is 248046.

640842 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (640837) and next prime (640847).

It is not an unprimeable number, because it can be changed into a prime (640847) by changing a digit.

640842 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 11 ways as a sum of consecutive naturals, for example, 4983 + ... + 5109.

It is an arithmetic number, because the mean of its divisors is an integer number (55744).

2⁶⁴⁰⁸⁴² is an apocalyptic number.

640842 is an abundant number, since it is smaller than the sum of its proper divisors (697014).

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

640842 is a wasteful number, since it uses less digits than its factorization.

640842 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 190 (or 161 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 24.

The square root of 640842 is about 800.5260770269. The cubic root of 640842 is about 86.2151634150.

Adding to 640842 its reverse (248046), we get a palindrome (888888).

The spelling of 640842 in words is "six hundred forty thousand, eight hundred forty-two".