131221021 has 2 divisors, whose sum is σ = 131221022. Its totient is φ = 131221020.

The previous prime is 131221009. The next prime is 131221037. The reversal of 131221021 is 120122131.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 115132900 + 16088121 = 10730^2 + 4011^2 .

It is a cyclic number.

It is not a de Polignac number, because 131221021 - 2⁵ = 131220989 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 131220992 and 131221010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (131221061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65610510 + 65610511.

It is an arithmetic number, because the mean of its divisors is an integer number (65610511).

Almost surely, 2^131221021 is an apocalyptic number.

It is an amenable number.

131221021 is a deficient number, since it is larger than the sum of its proper divisors (1).

131221021 is an equidigital number, since it uses as much as digits as its factorization.

131221021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24, while the sum is 13.

The square root of 131221021 is about 11455.1744203220. The cubic root of 131221021 is about 508.1607735591.

Adding to 131221021 its reverse (120122131), we get a palindrome (251343152).

The spelling of 131221021 in words is "one hundred thirty-one million, two hundred twenty-one thousand, twenty-one".