27721 has 4 divisors (see below), whose sum is σ = 29200. Its totient is φ = 26244.

The previous prime is 27701. The next prime is 27733. The reversal of 27721 is 12772.

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 4-Lehmer number, since φ(27721) divides (27721-1)⁴.

It is a cyclic number.

It is not a de Polignac number, because 27721 - 2⁵ = 27689 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19), and also a Moran number because the ratio is a prime number: 1459 = 27721 / (2 + 7 + 7 + 2 + 1).

It is a Duffinian number.

It is a nialpdrome in base 8 and base 15.

It is a zygodrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (27701) 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 3 ways as a sum of consecutive naturals, for example, 711 + ... + 748.

It is an arithmetic number, because the mean of its divisors is an integer number (7300).

2²⁷⁷²¹ is an apocalyptic number.

It is an amenable number.

27721 is a deficient number, since it is larger than the sum of its proper divisors (1479).

27721 is a wasteful number, since it uses less digits than its factorization.

27721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1478.

The product of its digits is 196, while the sum is 19.

The square root of 27721 is about 166.4962462039. The cubic root of 27721 is about 30.2646947251.

The spelling of 27721 in words is "twenty-seven thousand, seven hundred twenty-one", and thus it is an iban number.