81491833 has 2 divisors, whose sum is σ = 81491834. Its totient is φ = 81491832.

The previous prime is 81491801. The next prime is 81491881. The reversal of 81491833 is 33819418.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76510009 + 4981824 = 8747^2 + 2232^2 .

It is a cyclic number.

It is not a de Polignac number, because 81491833 - 2⁵ = 81491801 is a prime.

It is equal to p_4751569 and since 81491833 and 4751569 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 81491792 and 81491801.

It is not a weakly prime, because it can be changed into another prime (81491933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40745916 + 40745917.

It is an arithmetic number, because the mean of its divisors is an integer number (40745917).

Almost surely, 2^81491833 is an apocalyptic number.

It is an amenable number.

81491833 is a deficient number, since it is larger than the sum of its proper divisors (1).

81491833 is an equidigital number, since it uses as much as digits as its factorization.

81491833 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 37.

The square root of 81491833 is about 9027.2827030065. The cubic root of 81491833 is about 433.5488402743.

The spelling of 81491833 in words is "eighty-one million, four hundred ninety-one thousand, eight hundred thirty-three".