231721 has 6 divisors (see below), whose sum is σ = 269610. Its totient is φ = 198576.

The previous prime is 231719. The next prime is 231779. The reversal of 231721 is 127132.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 132496 + 99225 = 364^2 + 315^2 .

It is not a de Polignac number, because 231721 - 2¹ = 231719 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 231695 and 231704.

It is not an unprimeable number, because it can be changed into a prime (231701) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2316 + ... + 2413.

It is an arithmetic number, because the mean of its divisors is an integer number (44935).

2²³¹⁷²¹ is an apocalyptic number.

It is an amenable number.

231721 is a deficient number, since it is larger than the sum of its proper divisors (37889).

231721 is an equidigital number, since it uses as much as digits as its factorization.

231721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4743 (or 4736 counting only the distinct ones).

The product of its digits is 84, while the sum is 16.

The square root of 231721 is about 481.3740749147. The cubic root of 231721 is about 61.4216951277.

Adding to 231721 its reverse (127132), we get a palindrome (358853).

The spelling of 231721 in words is "two hundred thirty-one thousand, seven hundred twenty-one".