816643 has 4 divisors (see below), whose sum is σ = 825160. Its totient is φ = 808128.

The previous prime is 816593. The next prime is 816649. The reversal of 816643 is 346618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 346618 = 2 ⋅173309.

It is a cyclic number.

It is not a de Polignac number, because 816643 - 2⁹ = 816131 is a prime.

It is a Duffinian number.

816643 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (816649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4113 + ... + 4306.

It is an arithmetic number, because the mean of its divisors is an integer number (206290).

2⁸¹⁶⁶⁴³ is an apocalyptic number.

816643 is a deficient number, since it is larger than the sum of its proper divisors (8517).

816643 is an equidigital number, since it uses as much as digits as its factorization.

816643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8516.

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

The square root of 816643 is about 903.6830196479. The cubic root of 816643 is about 93.4711131177.

It can be divided in two parts, 81 and 6643, that added together give a square (6724 = 82²).

The spelling of 816643 in words is "eight hundred sixteen thousand, six hundred forty-three".