644654 has 4 divisors (see below), whose sum is σ = 966984. Its totient is φ = 322326.

The previous prime is 644653. The next prime is 644669. The reversal of 644654 is 456446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 456446 = 2 ⋅228223.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644654.

It is not an unprimeable number, because it can be changed into a prime (644653) 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 as a sum of consecutive naturals, namely, 161162 + ... + 161165.

It is an arithmetic number, because the mean of its divisors is an integer number (241746).

2⁶⁴⁴⁶⁵⁴ is an apocalyptic number.

644654 is a deficient number, since it is larger than the sum of its proper divisors (322330).

644654 is a wasteful number, since it uses less digits than its factorization.

644654 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322329.

The product of its digits is 11520, while the sum is 29.

The square root of 644654 is about 802.9034811234. The cubic root of 644654 is about 86.3857736922.

The spelling of 644654 in words is "six hundred forty-four thousand, six hundred fifty-four".