644998 has 8 divisors (see below), whose sum is σ = 970920. Its totient is φ = 321360.

The previous prime is 644977. The next prime is 644999. The reversal of 644998 is 899446.

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

It is a self number, because there is not a number n which added to its sum of digits gives 644998.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644999) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 733 + ... + 1351.

It is an arithmetic number, because the mean of its divisors is an integer number (121365).

2⁶⁴⁴⁹⁹⁸ is an apocalyptic number.

644998 is a deficient number, since it is larger than the sum of its proper divisors (325922).

644998 is a wasteful number, since it uses less digits than its factorization.

644998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1142.

The product of its digits is 62208, while the sum is 40.

The square root of 644998 is about 803.1176750639. The cubic root of 644998 is about 86.4011366734.

The spelling of 644998 in words is "six hundred forty-four thousand, nine hundred ninety-eight".