21893 has 2 divisors, whose sum is σ = 21894. Its totient is φ = 21892.

The previous prime is 21881. The next prime is 21911. The reversal of 21893 is 39812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20449 + 1444 = 143^2 + 38^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21893 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10946 + 10947.

It is an arithmetic number, because the mean of its divisors is an integer number (10947).

2²¹⁸⁹³ is an apocalyptic number.

It is an amenable number.

21893 is a deficient number, since it is larger than the sum of its proper divisors (1).

21893 is an equidigital number, since it uses as much as digits as its factorization.

21893 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432, while the sum is 23.

The square root of 21893 is about 147.9628331710. The cubic root of 21893 is about 27.9748924588.

The spelling of 21893 in words is "twenty-one thousand, eight hundred ninety-three".