643784 has 8 divisors (see below), whose sum is σ = 1207110. Its totient is φ = 321888.

The previous prime is 643781. The next prime is 643847. The reversal of 643784 is 487346.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 521284 + 122500 = 722^2 + 350^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 643784.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643784.

It is not an unprimeable number, because it can be changed into a prime (643781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40229 + ... + 40244.

2⁶⁴³⁷⁸⁴ is an apocalyptic number.

It is an amenable number.

643784 is a deficient number, since it is larger than the sum of its proper divisors (563326).

643784 is a wasteful number, since it uses less digits than its factorization.

643784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80479 (or 80475 counting only the distinct ones).

The product of its digits is 16128, while the sum is 32.

The square root of 643784 is about 802.3615145307. The cubic root of 643784 is about 86.3468952357.

The spelling of 643784 in words is "six hundred forty-three thousand, seven hundred eighty-four".