27661 has 4 divisors (see below), whose sum is σ = 28000. Its totient is φ = 27324.

The previous prime is 27653. The next prime is 27673. The reversal of 27661 is 16672.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 27661 - 2³ = 27653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27611) 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, 40 + ... + 238.

It is an arithmetic number, because the mean of its divisors is an integer number (7000).

2²⁷⁶⁶¹ is an apocalyptic number.

It is an amenable number.

27661 is a deficient number, since it is larger than the sum of its proper divisors (339).

27661 is a wasteful number, since it uses less digits than its factorization.

27661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 338.

The product of its digits is 504, while the sum is 22.

The square root of 27661 is about 166.3159643570. The cubic root of 27661 is about 30.2428437412.

It can be divided in two parts, 276 and 61, that multiplied together give a triangular number (16836 = T₁₈₃).

The spelling of 27661 in words is "twenty-seven thousand, six hundred sixty-one".