643736 has 16 divisors (see below), whose sum is σ = 1226040. Its totient is φ = 316800.

The previous prime is 643729. The next prime is 643751. The reversal of 643736 is 637346.

It is a junction number, because it is equal to n+sod(n) for n = 643699 and 643708.

It is a congruent number.

It is an unprimeable number.

643736 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65 + ... + 1136.

2⁶⁴³⁷³⁶ is an apocalyptic number.

It is an amenable number.

643736 is a deficient number, since it is larger than the sum of its proper divisors (582304).

643736 is a wasteful number, since it uses less digits than its factorization.

643736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1274 (or 1270 counting only the distinct ones).

The product of its digits is 9072, while the sum is 29.

The square root of 643736 is about 802.3316022693. The cubic root of 643736 is about 86.3447491981.

The spelling of 643736 in words is "six hundred forty-three thousand, seven hundred thirty-six".