81938491 has 2 divisors, whose sum is σ = 81938492. Its totient is φ = 81938490.

The previous prime is 81938429. The next prime is 81938497. The reversal of 81938491 is 19483918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81938491 - 2⁹ = 81937979 is a prime.

It is not a weakly prime, because it can be changed into another prime (81938497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40969245 + 40969246.

It is an arithmetic number, because the mean of its divisors is an integer number (40969246).

Almost surely, 2^81938491 is an apocalyptic number.

81938491 is a deficient number, since it is larger than the sum of its proper divisors (1).

81938491 is an equidigital number, since it uses as much as digits as its factorization.

81938491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 43.

The square root of 81938491 is about 9051.9882346366. The cubic root of 81938491 is about 434.3394934730.

The spelling of 81938491 in words is "eighty-one million, nine hundred thirty-eight thousand, four hundred ninety-one".