644078 has 4 divisors (see below), whose sum is σ = 966120. Its totient is φ = 322038.

The previous prime is 644057. The next prime is 644089. The reversal of 644078 is 870446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 870446 = 2 ⋅435223.

It is a self number, because there is not a number n which added to its sum of digits gives 644078.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161018 + ... + 161021.

It is an arithmetic number, because the mean of its divisors is an integer number (241530).

2⁶⁴⁴⁰⁷⁸ is an apocalyptic number.

644078 is a deficient number, since it is larger than the sum of its proper divisors (322042).

644078 is a wasteful number, since it uses less digits than its factorization.

644078 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322041.

The product of its (nonzero) digits is 5376, while the sum is 29.

The square root of 644078 is about 802.5447028048. The cubic root of 644078 is about 86.3600373888.

The spelling of 644078 in words is "six hundred forty-four thousand, seventy-eight".