81643 has 4 divisors (see below), whose sum is σ = 85960. Its totient is φ = 77328.

The previous prime is 81637. The next prime is 81647. The reversal of 81643 is 34618.

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

It is a cyclic number.

It is not a de Polignac number, because 81643 - 2⁵ = 81611 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81647) 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, 2130 + ... + 2167.

It is an arithmetic number, because the mean of its divisors is an integer number (21490).

2⁸¹⁶⁴³ is an apocalyptic number.

81643 is a deficient number, since it is larger than the sum of its proper divisors (4317).

81643 is a wasteful number, since it uses less digits than its factorization.

81643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4316.

The product of its digits is 576, while the sum is 22.

The square root of 81643 is about 285.7323922834. The cubic root of 81643 is about 43.3816751763.

The spelling of 81643 in words is "eighty-one thousand, six hundred forty-three".