640042 has 16 divisors (see below), whose sum is σ = 1048320. Its totient is φ = 291312.

The previous prime is 640039. The next prime is 640043. The reversal of 640042 is 240046.

It is a nialpdrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 639998 and 640025.

It is not an unprimeable number, because it can be changed into a prime (640043) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2559 + ... + 2797.

It is an arithmetic number, because the mean of its divisors is an integer number (65520).

2⁶⁴⁰⁰⁴² is an apocalyptic number.

640042 is a deficient number, since it is larger than the sum of its proper divisors (408278).

640042 is a wasteful number, since it uses less digits than its factorization.

640042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 357.

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 640042 is about 800.0262495694. The cubic root of 640042 is about 86.1792726904.

Adding to 640042 its reverse (240046), we get a palindrome (880088).

The spelling of 640042 in words is "six hundred forty thousand, forty-two".