21943 has 2 divisors, whose sum is σ = 21944. Its totient is φ = 21942.

The previous prime is 21937. The next prime is 21961. The reversal of 21943 is 34912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21943 - 2⁵ = 21911 is a prime.

It is a plaindrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 21943.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10971 + 10972.

It is an arithmetic number, because the mean of its divisors is an integer number (10972).

21943 is a Friedman number, since it can be written as (14*2)^3-9, using all its digits and the basic arithmetic operations.

2²¹⁹⁴³ is an apocalyptic number.

21943 is a deficient number, since it is larger than the sum of its proper divisors (1).

21943 is an equidigital number, since it uses as much as digits as its factorization.

21943 is an evil number, because the sum of its binary digits is even.

The product of its digits is 216, while the sum is 19.

The square root of 21943 is about 148.1316981608. The cubic root of 21943 is about 27.9961729463.

It can be divided in two parts, 2194 and 3, that added together give a cube (2197 = 13³).

The spelling of 21943 in words is "twenty-one thousand, nine hundred forty-three".