643716 has 18 divisors (see below), whose sum is σ = 1627262. Its totient is φ = 214560.

The previous prime is 643703. The next prime is 643723. The reversal of 643716 is 617346.

643716 is a `hidden beast` number, since 643 + 7 + 16 = 666.

It can be written as a sum of positive squares in only one way, i.e., 518400 + 125316 = 720^2 + 354^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a self number, because there is not a number n which added to its sum of digits gives 643716.

It is an unprimeable number.

643716 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 5 ways as a sum of consecutive naturals, for example, 8905 + ... + 8976.

2⁶⁴³⁷¹⁶ is an apocalyptic number.

It is an amenable number.

643716 is an abundant number, since it is smaller than the sum of its proper divisors (983546).

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

643716 is a wasteful number, since it uses less digits than its factorization.

643716 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17891 (or 17886 counting only the distinct ones).

The product of its digits is 3024, while the sum is 27.

The square root of 643716 is about 802.3191384979. The cubic root of 643716 is about 86.3438549843.

The spelling of 643716 in words is "six hundred forty-three thousand, seven hundred sixteen".