643776 has 56 divisors (see below), whose sum is σ = 1950720. Its totient is φ = 183552.

The previous prime is 643751. The next prime is 643781. The reversal of 643776 is 677346.

It is a tau number, because it is divible by the number of its divisors (56).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1105 + ... + 1583.

2⁶⁴³⁷⁷⁶ 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 643776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (975360).

643776 is an abundant number, since it is smaller than the sum of its proper divisors (1306944).

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

643776 is a wasteful number, since it uses less digits than its factorization.

643776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 501 (or 491 counting only the distinct ones).

The product of its digits is 21168, while the sum is 33.

The square root of 643776 is about 802.3565292312. The cubic root of 643776 is about 86.3465375702.

The spelling of 643776 in words is "six hundred forty-three thousand, seven hundred seventy-six".