21773 has 2 divisors, whose sum is σ = 21774. Its totient is φ = 21772.

The previous prime is 21767. The next prime is 21787. The reversal of 21773 is 37712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14884 + 6889 = 122^2 + 83^2 .

It is a cyclic number.

It is not a de Polignac number, because 21773 - 2⁴ = 21757 is a prime.

It is a plaindrome in base 6.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21713) 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, 10886 + 10887.

It is an arithmetic number, because the mean of its divisors is an integer number (10887).

2²¹⁷⁷³ is an apocalyptic number.

It is an amenable number.

21773 is a deficient number, since it is larger than the sum of its proper divisors (1).

21773 is an equidigital number, since it uses as much as digits as its factorization.

21773 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 294, while the sum is 20.

The square root of 21773 is about 147.5567687366. The cubic root of 21773 is about 27.9236867571.

The spelling of 21773 in words is "twenty-one thousand, seven hundred seventy-three", and thus it is an iban number.