644642 has 8 divisors (see below), whose sum is σ = 973596. Its totient is φ = 320112.

The previous prime is 644629. The next prime is 644647. The reversal of 644642 is 246446.

It can be written as a sum of positive squares in 2 ways, for example, as 638401 + 6241 = 799^2 + 79^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (644647) by changing a digit.

644642 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 3 ways as a sum of consecutive naturals, for example, 713 + ... + 1340.

2⁶⁴⁴⁶⁴² is an apocalyptic number.

644642 is a deficient number, since it is larger than the sum of its proper divisors (328954).

644642 is a wasteful number, since it uses less digits than its factorization.

644642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2212.

The product of its digits is 4608, while the sum is 26.

The square root of 644642 is about 802.8960082103. The cubic root of 644642 is about 86.3852376756.

The spelling of 644642 in words is "six hundred forty-four thousand, six hundred forty-two".