133581 has 8 divisors (see below), whose sum is σ = 203584. Its totient is φ = 76320.

The previous prime is 133571. The next prime is 133583. The reversal of 133581 is 185331.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 133581 - 2⁹ = 133069 is a prime.

It is a super-2 number, since 2×133581² = 35687767122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 6361 = 133581 / (1 + 3 + 3 + 5 + 8 + 1).

It is a Duffinian number.

133581 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (133583) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3160 + ... + 3201.

It is an arithmetic number, because the mean of its divisors is an integer number (25448).

2¹³³⁵⁸¹ is an apocalyptic number.

It is an amenable number.

133581 is a deficient number, since it is larger than the sum of its proper divisors (70003).

133581 is an equidigital number, since it uses as much as digits as its factorization.

133581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6371.

The product of its digits is 360, while the sum is 21.

The square root of 133581 is about 365.4873458822. The cubic root of 133581 is about 51.1189074783.

The spelling of 133581 in words is "one hundred thirty-three thousand, five hundred eighty-one".