71561 has 4 divisors (see below), whose sum is σ = 81792. Its totient is φ = 61332.

The previous prime is 71551. The next prime is 71563. The reversal of 71561 is 16517.

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 an emirpimes, since its reverse is a distinct semiprime: 16517 = 83 ⋅199.

It is a cyclic number.

It is not a de Polignac number, because 71561 - 2¹⁰ = 70537 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (71563) 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, 5105 + ... + 5118.

It is an arithmetic number, because the mean of its divisors is an integer number (20448).

2⁷¹⁵⁶¹ is an apocalyptic number.

It is an amenable number.

71561 is a deficient number, since it is larger than the sum of its proper divisors (10231).

71561 is a wasteful number, since it uses less digits than its factorization.

71561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10230.

The product of its digits is 210, while the sum is 20.

The square root of 71561 is about 267.5088783573. The cubic root of 71561 is about 41.5169524780.

The spelling of 71561 in words is "seventy-one thousand, five hundred sixty-one".