81371881 has 2 divisors, whose sum is σ = 81371882. Its totient is φ = 81371880.

The previous prime is 81371863. The next prime is 81371897. The reversal of 81371881 is 18817318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78481881 + 2890000 = 8859^2 + 1700^2 .

It is a cyclic number.

It is not a de Polignac number, because 81371881 - 2⁷ = 81371753 is a prime.

It is a super-2 number, since 2×81371881² = 13242766034956322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81371881.

It is not a weakly prime, because it can be changed into another prime (81371581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40685940 + 40685941.

It is an arithmetic number, because the mean of its divisors is an integer number (40685941).

Almost surely, 2^81371881 is an apocalyptic number.

It is an amenable number.

81371881 is a deficient number, since it is larger than the sum of its proper divisors (1).

81371881 is an equidigital number, since it uses as much as digits as its factorization.

81371881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10752, while the sum is 37.

The square root of 81371881 is about 9020.6363966186. The cubic root of 81371881 is about 433.3360149078.

The spelling of 81371881 in words is "eighty-one million, three hundred seventy-one thousand, eight hundred eighty-one".