21767 has 2 divisors, whose sum is σ = 21768. Its totient is φ = 21766.

The previous prime is 21757. The next prime is 21773. The reversal of 21767 is 76712.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21767 - 2⁴ = 21751 is a prime.

It is a Chen prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21767.

It is not a weakly prime, because it can be changed into another prime (21727) 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, 10883 + 10884.

It is an arithmetic number, because the mean of its divisors is an integer number (10884).

2²¹⁷⁶⁷ is an apocalyptic number.

21767 is a deficient number, since it is larger than the sum of its proper divisors (1).

21767 is an equidigital number, since it uses as much as digits as its factorization.

21767 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 588, while the sum is 23.

The square root of 21767 is about 147.5364361776. The cubic root of 21767 is about 27.9211215385.

Subtracting 21767 from its reverse (76712), we obtain a palindrome (54945).

The spelling of 21767 in words is "twenty-one thousand, seven hundred sixty-seven".