644042 has 16 divisors (see below), whose sum is σ = 1114560. Its totient is φ = 273408.

The previous prime is 644029. The next prime is 644047. The reversal of 644042 is 240446.

It is not an unprimeable number, because it can be changed into a prime (644047) by changing a digit.

644042 is an untouchable number, because it is not equal to the sum of proper divisors of any 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, 2378 + ... + 2634.

It is an arithmetic number, because the mean of its divisors is an integer number (69660).

2⁶⁴⁴⁰⁴² is an apocalyptic number.

644042 is a deficient number, since it is larger than the sum of its proper divisors (470518).

644042 is a wasteful number, since it uses less digits than its factorization.

644042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 445.

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

The square root of 644042 is about 802.5222738342. The cubic root of 644042 is about 86.3584283605.

Adding to 644042 its reverse (240446), we get a palindrome (884488).

It can be divided in two parts, 6440 and 42, that multiplied together give a triangular number (270480 = T₇₃₅).

The spelling of 644042 in words is "six hundred forty-four thousand, forty-two".