640942 has 4 divisors (see below), whose sum is σ = 961416. Its totient is φ = 320470.

The previous prime is 640933. The next prime is 640943. The reversal of 640942 is 249046.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640943) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160234 + ... + 160237.

It is an arithmetic number, because the mean of its divisors is an integer number (240354).

2⁶⁴⁰⁹⁴² is an apocalyptic number.

640942 is a deficient number, since it is larger than the sum of its proper divisors (320474).

640942 is a wasteful number, since it uses less digits than its factorization.

640942 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320473.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 640942 is about 800.5885335177. The cubic root of 640942 is about 86.2196476550.

Adding to 640942 its reverse (249046), we get a palindrome (889988).

The spelling of 640942 in words is "six hundred forty thousand, nine hundred forty-two".