131891209 has 2 divisors, whose sum is σ = 131891210. Its totient is φ = 131891208.

The previous prime is 131891173. The next prime is 131891231. The reversal of 131891209 is 902198131.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 90250000 + 41641209 = 9500^2 + 6453^2 .

It is a cyclic number.

It is not a de Polignac number, because 131891209 - 2⁹ = 131890697 is a prime.

It is a super-2 number, since 2×131891209² = 34790582022963362, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (131891239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65945604 + 65945605.

It is an arithmetic number, because the mean of its divisors is an integer number (65945605).

Almost surely, 2^131891209 is an apocalyptic number.

It is an amenable number.

131891209 is a deficient number, since it is larger than the sum of its proper divisors (1).

131891209 is an equidigital number, since it uses as much as digits as its factorization.

131891209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 34.

The square root of 131891209 is about 11484.3897965891. The cubic root of 131891209 is about 509.0244184759.

The spelling of 131891209 in words is "one hundred thirty-one million, eight hundred ninety-one thousand, two hundred nine".