81491135933 has 2 divisors, whose sum is σ = 81491135934. Its totient is φ = 81491135932.

The previous prime is 81491135923. The next prime is 81491135953. The reversal of 81491135933 is 33953119418.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 79094250169 + 2396885764 = 281237^2 + 48958^2 .

It is a cyclic number.

It is not a de Polignac number, because 81491135933 - 2⁴ = 81491135917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81491135923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40745567966 + 40745567967.

It is an arithmetic number, because the mean of its divisors is an integer number (40745567967).

Almost surely, 2^81491135933 is an apocalyptic number.

It is an amenable number.

81491135933 is a deficient number, since it is larger than the sum of its proper divisors (1).

81491135933 is an equidigital number, since it uses as much as digits as its factorization.

81491135933 is an evil number, because the sum of its binary digits is even.

The product of its digits is 349920, while the sum is 47.

The spelling of 81491135933 in words is "eighty-one billion, four hundred ninety-one million, one hundred thirty-five thousand, nine hundred thirty-three".