81371491 has 2 divisors, whose sum is σ = 81371492. Its totient is φ = 81371490.

The previous prime is 81371489. The next prime is 81371519. The reversal of 81371491 is 19417318.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81371491 - 2¹ = 81371489 is a prime.

Together with 81371489, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81371461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40685745 + 40685746.

It is an arithmetic number, because the mean of its divisors is an integer number (40685746).

Almost surely, 2^81371491 is an apocalyptic number.

81371491 is a deficient number, since it is larger than the sum of its proper divisors (1).

81371491 is an equidigital number, since it uses as much as digits as its factorization.

81371491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6048, while the sum is 34.

The square root of 81371491 is about 9020.6147794926. The cubic root of 81371491 is about 433.3353226076.

The spelling of 81371491 in words is "eighty-one million, three hundred seventy-one thousand, four hundred ninety-one".