20843 has 4 divisors (see below), whose sum is σ = 21960. Its totient is φ = 19728.

The previous prime is 20809. The next prime is 20849. The reversal of 20843 is 34802.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 34802 = 2 ⋅17401.

It is a cyclic number.

It is not a de Polignac number, because 20843 - 2¹⁰ = 19819 is a prime.

It is a d-powerful number, because it can be written as 2⁷ + 0 + 8 + 4⁵ + 3⁹ .

It is a Duffinian number.

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (20849) 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, 530 + ... + 567.

It is an arithmetic number, because the mean of its divisors is an integer number (5490).

2²⁰⁸⁴³ is an apocalyptic number.

20843 is a deficient number, since it is larger than the sum of its proper divisors (1117).

20843 is a wasteful number, since it uses less digits than its factorization.

20843 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1116.

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 20843 is about 144.3710497295. The cubic root of 20843 is about 27.5203155667.

The spelling of 20843 in words is "twenty thousand, eight hundred forty-three".