643648 has 28 divisors (see below), whose sum is σ = 1303020. Its totient is φ = 315392.

The previous prime is 643639. The next prime is 643649. The reversal of 643648 is 846346.

It can be written as a sum of positive squares in 2 ways, for example, as 53824 + 589824 = 232^2 + 768^2 .

It is not an unprimeable number, because it can be changed into a prime (643649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5640 + ... + 5752.

2⁶⁴³⁶⁴⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (651510).

643648 is an abundant number, since it is smaller than the sum of its proper divisors (659372).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

643648 is a wasteful number, since it uses less digits than its factorization.

643648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214 (or 204 counting only the distinct ones).

The product of its digits is 13824, while the sum is 31.

The square root of 643648 is about 802.2767602268. The cubic root of 643648 is about 86.3408145188.

The spelling of 643648 in words is "six hundred forty-three thousand, six hundred forty-eight".