643816 has 16 divisors (see below), whose sum is σ = 1260000. Its totient is φ = 307824.

The previous prime is 643781. The next prime is 643847. The reversal of 643816 is 618346.

643816 = T₁₉ + T₂₀ + ... + T₁₅₆.

643816 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1566 + ... + 1933.

It is an arithmetic number, because the mean of its divisors is an integer number (78750).

2⁶⁴³⁸¹⁶ is an apocalyptic number.

It is an amenable number.

643816 is a deficient number, since it is larger than the sum of its proper divisors (616184).

643816 is a wasteful number, since it uses less digits than its factorization.

643816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3528 (or 3524 counting only the distinct ones).

The product of its digits is 3456, while the sum is 28.

The square root of 643816 is about 802.3814554188. The cubic root of 643816 is about 86.3483258681.

The spelling of 643816 in words is "six hundred forty-three thousand, eight hundred sixteen".