644618 has 8 divisors (see below), whose sum is σ = 1041348. Its totient is φ = 297504.

The previous prime is 644617. The next prime is 644629. The reversal of 644618 is 816446.

It can be written as a sum of positive squares in 2 ways, for example, as 635209 + 9409 = 797^2 + 97^2 .

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (644617) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12371 + ... + 12422.

2⁶⁴⁴⁶¹⁸ is an apocalyptic number.

644618 is a deficient number, since it is larger than the sum of its proper divisors (396730).

644618 is a wasteful number, since it uses less digits than its factorization.

644618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24808.

The product of its digits is 4608, while the sum is 29.

The square root of 644618 is about 802.8810621755. The cubic root of 644618 is about 86.3841656225.

The spelling of 644618 in words is "six hundred forty-four thousand, six hundred eighteen".