133661 has 8 divisors (see below), whose sum is σ = 151200. Its totient is φ = 117040.

The previous prime is 133657. The next prime is 133669. The reversal of 133661 is 166331.

133661 = T₇₃ + T₇₄ + ... + T₁₀₅.

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

It is not a de Polignac number, because 133661 - 2² = 133657 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 (133669) 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 7 ways as a sum of consecutive naturals, for example, 110 + ... + 528.

It is an arithmetic number, because the mean of its divisors is an integer number (18900).

2¹³³⁶⁶¹ is an apocalyptic number.

133661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

133661 is the 164-th centered decagonal number.

It is an amenable number.

133661 is a deficient number, since it is larger than the sum of its proper divisors (17539).

133661 is a wasteful number, since it uses less digits than its factorization.

133661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 459.

The product of its digits is 324, while the sum is 20.

The square root of 133661 is about 365.5967724146. The cubic root of 133661 is about 51.1291102679.

Adding to 133661 its reverse (166331), we get a palindrome (299992).

The spelling of 133661 in words is "one hundred thirty-three thousand, six hundred sixty-one".