133721 has 6 divisors (see below), whose sum is σ = 155610. Its totient is φ = 114576.

The previous prime is 133717. The next prime is 133723. The reversal of 133721 is 127331.

It can be written as a sum of positive squares in only one way, i.e., 132496 + 1225 = 364^2 + 35^2 .

It is not a de Polignac number, because 133721 - 2² = 133717 is a prime.

It is an Ulam number.

It is a d-powerful number, because it can be written as 1 + 3 + 7⁴ + 3⁵ + 2¹⁷ + 1 .

It is a plaindrome in base 9.

It is a self number, because there is not a number n which added to its sum of digits gives 133721.

It is not an unprimeable number, because it can be changed into a prime (133723) 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 5 ways as a sum of consecutive naturals, for example, 1316 + ... + 1413.

It is an arithmetic number, because the mean of its divisors is an integer number (25935).

2¹³³⁷²¹ is an apocalyptic number.

It is an amenable number.

133721 is a deficient number, since it is larger than the sum of its proper divisors (21889).

133721 is an equidigital number, since it uses as much as digits as its factorization.

133721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2743 (or 2736 counting only the distinct ones).

The product of its digits is 126, while the sum is 17.

The square root of 133721 is about 365.6788208251. The cubic root of 133721 is about 51.1367596887.

The spelling of 133721 in words is "one hundred thirty-three thousand, seven hundred twenty-one".