133561 has 4 divisors (see below), whose sum is σ = 139392. Its totient is φ = 127732.

The previous prime is 133559. The next prime is 133571. The reversal of 133561 is 165331.

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 cyclic number.

It is not a de Polignac number, because 133561 - 2¹ = 133559 is a prime.

It is a Duffinian number.

133561 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (133541) 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, 2881 + ... + 2926.

It is an arithmetic number, because the mean of its divisors is an integer number (34848).

2¹³³⁵⁶¹ is an apocalyptic number.

It is an amenable number.

133561 is a deficient number, since it is larger than the sum of its proper divisors (5831).

133561 is an equidigital number, since it uses as much as digits as its factorization.

133561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5830.

The product of its digits is 270, while the sum is 19.

The square root of 133561 is about 365.4599841296. The cubic root of 133561 is about 51.1163561445.

Adding to 133561 its reverse (165331), we get a palindrome (298892).

The spelling of 133561 in words is "one hundred thirty-three thousand, five hundred sixty-one".