131861 has 2 divisors, whose sum is σ = 131862. Its totient is φ = 131860.

The previous prime is 131849. The next prime is 131891. The reversal of 131861 is 168131.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78961 + 52900 = 281^2 + 230^2 .

It is a cyclic number.

It is not a de Polignac number, because 131861 - 2⁶ = 131797 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (131891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65930 + 65931.

It is an arithmetic number, because the mean of its divisors is an integer number (65931).

2¹³¹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

131861 is a deficient number, since it is larger than the sum of its proper divisors (1).

131861 is an equidigital number, since it uses as much as digits as its factorization.

131861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 144, while the sum is 20.

The square root of 131861 is about 363.1266996518. The cubic root of 131861 is about 50.8985552371.

Subtracting from 131861 its sum of digits (20), we obtain a triangular number (131841 = T₅₁₃).

Adding to 131861 its reverse (168131), we get a palindrome (299992).

The spelling of 131861 in words is "one hundred thirty-one thousand, eight hundred sixty-one".