2131211981 has 2 divisors, whose sum is σ = 2131211982. Its totient is φ = 2131211980.

The previous prime is 2131211959. The next prime is 2131211989. The reversal of 2131211981 is 1891121312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2128991881 + 2220100 = 46141^2 + 1490^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2131211981 is a prime.

It is a super-2 number, since 2×2131211981² = 9084129015915888722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2131211989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1065605990 + 1065605991.

It is an arithmetic number, because the mean of its divisors is an integer number (1065605991).

Almost surely, 2^2131211981 is an apocalyptic number.

It is an amenable number.

2131211981 is a deficient number, since it is larger than the sum of its proper divisors (1).

2131211981 is an equidigital number, since it uses as much as digits as its factorization.

2131211981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864, while the sum is 29.

The square root of 2131211981 is about 46165.0515108561. The cubic root of 2131211981 is about 1286.8923414712.

The spelling of 2131211981 in words is "two billion, one hundred thirty-one million, two hundred eleven thousand, nine hundred eighty-one".