131221212181 has 2 divisors, whose sum is σ = 131221212182. Its totient is φ = 131221212180.

The previous prime is 131221212169. The next prime is 131221212203. The reversal of 131221212181 is 181212122131.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 107862980625 + 23358231556 = 328425^2 + 152834^2 .

It is an emirp because it is prime and its reverse (181212122131) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 131221212181 - 2⁵ = 131221212149 is a prime.

It is a super-2 number, since 2×131221212181² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (131221212121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65610606090 + 65610606091.

It is an arithmetic number, because the mean of its divisors is an integer number (65610606091).

Almost surely, 2^131221212181 is an apocalyptic number.

It is an amenable number.

131221212181 is a deficient number, since it is larger than the sum of its proper divisors (1).

131221212181 is an equidigital number, since it uses as much as digits as its factorization.

131221212181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 384, while the sum is 25.

The spelling of 131221212181 in words is "one hundred thirty-one billion, two hundred twenty-one million, two hundred twelve thousand, one hundred eighty-one".