21776 has 10 divisors (see below), whose sum is σ = 42222. Its totient is φ = 10880.

The previous prime is 21773. The next prime is 21787. The reversal of 21776 is 67712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 15376 + 6400 = 124^2 + 80^2 .

It is a plaindrome in base 15.

It is a nialpdrome in base 16.

It is a zygodrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (21773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 665 + ... + 696.

2²¹⁷⁷⁶ is an apocalyptic number.

It is an amenable number.

21776 is a deficient number, since it is larger than the sum of its proper divisors (20446).

21776 is a wasteful number, since it uses less digits than its factorization.

21776 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1369 (or 1363 counting only the distinct ones).

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

The square root of 21776 is about 147.5669339656. The cubic root of 21776 is about 27.9249691897.

It can be divided in two parts, 21 and 776, that added together give a palindrome (797).

The spelling of 21776 in words is "twenty-one thousand, seven hundred seventy-six".