131221 has 2 divisors, whose sum is σ = 131222. Its totient is φ = 131220.

The previous prime is 131213. The next prime is 131231. The reversal of 131221 is 122131.

It is an a-pointer prime, because the next prime (131231) can be obtained adding 131221 to its sum of digits (10).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 130321 + 900 = 361^2 + 30^2 .

It is an emirp because it is prime and its reverse (122131) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 131221 - 2³ = 131213 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 131198 and 131207.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (131231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65610 + 65611.

It is an arithmetic number, because the mean of its divisors is an integer number (65611).

2¹³¹²²¹ is an apocalyptic number.

It is an amenable number.

131221 is a deficient number, since it is larger than the sum of its proper divisors (1).

131221 is an equidigital number, since it uses as much as digits as its factorization.

131221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12, while the sum is 10.

The square root of 131221 is about 362.2443926412. The cubic root of 131221 is about 50.8160746451.

Adding to 131221 its reverse (122131), we get a palindrome (253352).

The spelling of 131221 in words is "one hundred thirty-one thousand, two hundred twenty-one".