643822 has 4 divisors (see below), whose sum is σ = 965736. Its totient is φ = 321910.

The previous prime is 643781. The next prime is 643847. The reversal of 643822 is 228346.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is an unprimeable number.

643822 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 as a sum of consecutive naturals, namely, 160954 + ... + 160957.

It is an arithmetic number, because the mean of its divisors is an integer number (241434).

2⁶⁴³⁸²² is an apocalyptic number.

643822 is a deficient number, since it is larger than the sum of its proper divisors (321914).

643822 is a wasteful number, since it uses less digits than its factorization.

643822 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321913.

The product of its digits is 2304, while the sum is 25.

The square root of 643822 is about 802.3851942802. The cubic root of 643822 is about 86.3485941065.

The spelling of 643822 in words is "six hundred forty-three thousand, eight hundred twenty-two".