231661 has 2 divisors, whose sum is σ = 231662. Its totient is φ = 231660.

The previous prime is 231643. The next prime is 231677. The reversal of 231661 is 166132.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 189225 + 42436 = 435^2 + 206^2 .

It is a cyclic number.

It is not a de Polignac number, because 231661 - 2⁷ = 231533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115830 + 115831.

It is an arithmetic number, because the mean of its divisors is an integer number (115831).

2²³¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

231661 is a deficient number, since it is larger than the sum of its proper divisors (1).

231661 is an equidigital number, since it uses as much as digits as its factorization.

231661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 216, while the sum is 19.

The square root of 231661 is about 481.3117492852. The cubic root of 231661 is about 61.4163933210.

Adding to 231661 its reverse (166132), we get a palindrome (397793).

The spelling of 231661 in words is "two hundred thirty-one thousand, six hundred sixty-one".