644068 has 6 divisors (see below), whose sum is σ = 1127126. Its totient is φ = 322032.

The previous prime is 644057. The next prime is 644089. The reversal of 644068 is 860446.

It can be written as a sum of positive squares in only one way, i.e., 381924 + 262144 = 618^2 + 512^2 .

It is an Ulam number.

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 as a sum of consecutive naturals, namely, 80505 + ... + 80512.

2⁶⁴⁴⁰⁶⁸ is an apocalyptic number.

It is an amenable number.

644068 is a deficient number, since it is larger than the sum of its proper divisors (483058).

644068 is a wasteful number, since it uses less digits than its factorization.

644068 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161021 (or 161019 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 644068 is about 802.5384725980. The cubic root of 644068 is about 86.3595904425.

The spelling of 644068 in words is "six hundred forty-four thousand, sixty-eight".