21769 has 4 divisors (see below), whose sum is σ = 23760. Its totient is φ = 19780.

The previous prime is 21767. The next prime is 21773. The reversal of 21769 is 96712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21769 - 2¹ = 21767 is a prime.

It is a super-2 number, since 2×21769² = 947778722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21767) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 979 + ... + 1000.

It is an arithmetic number, because the mean of its divisors is an integer number (5940).

2²¹⁷⁶⁹ is an apocalyptic number.

It is an amenable number.

21769 is a deficient number, since it is larger than the sum of its proper divisors (1991).

21769 is a wasteful number, since it uses less digits than its factorization.

21769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1990.

The product of its digits is 756, while the sum is 25.

The square root of 21769 is about 147.5432140086. The cubic root of 21769 is about 27.9219766637.

It can be divided in two parts, 2 and 1769, that added together give a palindrome (1771).

The spelling of 21769 in words is "twenty-one thousand, seven hundred sixty-nine".