5561 has 4 divisors (see below), whose sum is σ = 5712. Its totient is φ = 5412.

The previous prime is 5557. The next prime is 5563. The reversal of 5561 is 1655.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1655 = 5 ⋅331.

It is a cyclic number.

It is not a de Polignac number, because 5561 - 2² = 5557 is a prime.

It is a Duffinian number.

Its product of digits (150) is a multiple of the sum of its prime divisors (150).

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (5563) 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, 26 + ... + 108.

It is an arithmetic number, because the mean of its divisors is an integer number (1428).

2⁵⁵⁶¹ is an apocalyptic number.

It is an amenable number.

5561 is a deficient number, since it is larger than the sum of its proper divisors (151).

5561 is an equidigital number, since it uses as much as digits as its factorization.

With its predecessor (5560) it forms a Ruth-Aaron pair, since the sum of their prime factors is the same (150).

5561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150.

The product of its digits is 150, while the sum is 17.

The square root of 5561 is about 74.5721127500. The cubic root of 5561 is about 17.7167598497.

The spelling of 5561 in words is "five thousand, five hundred sixty-one".