21774 has 16 divisors (see below), whose sum is σ = 46080. Its totient is φ = 6840.

The previous prime is 21773. The next prime is 21787. The reversal of 21774 is 47712.

It is a self number, because there is not a number n which added to its sum of digits gives 21774.

It is a congruent number.

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 (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19 + ... + 209.

It is an arithmetic number, because the mean of its divisors is an integer number (2880).

2²¹⁷⁷⁴ is an apocalyptic number.

21774 is an abundant number, since it is smaller than the sum of its proper divisors (24306).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23040).

21774 is a wasteful number, since it uses less digits than its factorization.

21774 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215.

The product of its digits is 392, while the sum is 21.

The square root of 21774 is about 147.5601572241. The cubic root of 21774 is about 27.9241142477.

The spelling of 21774 in words is "twenty-one thousand, seven hundred seventy-four", and thus it is an iban number.