643916 has 48 divisors (see below), whose sum is σ = 1458240. Its totient is φ = 241920.

The previous prime is 643889. The next prime is 643919. The reversal of 643916 is 619346.

643916 = 109² + 110² + ... + 147².

643916 is nontrivially palindromic in base 5.

643916 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is not an unprimeable number, because it can be changed into a prime (643919) by changing a digit.

643916 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 15 ways as a sum of consecutive naturals, for example, 10526 + ... + 10586.

It is an arithmetic number, because the mean of its divisors is an integer number (30380).

2⁶⁴³⁹¹⁶ 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 643916, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (729120).

643916 is an abundant number, since it is smaller than the sum of its proper divisors (814324).

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

643916 is a wasteful number, since it uses less digits than its factorization.

643916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114 (or 112 counting only the distinct ones).

The product of its digits is 3888, while the sum is 29.

The square root of 643916 is about 802.4437675003. The cubic root of 643916 is about 86.3527962891.

The spelling of 643916 in words is "six hundred forty-three thousand, nine hundred sixteen".