640442 has 16 divisors (see below), whose sum is σ = 1073952. Its totient is φ = 283920.

The previous prime is 640421. The next prime is 640457. The reversal of 640442 is 244046.

It is a super-4 number, since 4×640442⁴ (a number of 24 digits) contains 4444 as substring.

It is an unprimeable number.

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, 608 + ... + 1284.

It is an arithmetic number, because the mean of its divisors is an integer number (67122).

2⁶⁴⁰⁴⁴² is an apocalyptic number.

640442 is a deficient number, since it is larger than the sum of its proper divisors (433510).

640442 is a wasteful number, since it uses less digits than its factorization.

640442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 733.

The product of its (nonzero) digits is 768, while the sum is 20.

The square root of 640442 is about 800.2762023202. The cubic root of 640442 is about 86.1972217888.

Adding to 640442 its reverse (244046), we get a palindrome (884488).

It can be divided in two parts, 64044 and 2, that added together give a palindrome (64046).

The spelling of 640442 in words is "six hundred forty thousand, four hundred forty-two".