81775891 has 2 divisors, whose sum is σ = 81775892. Its totient is φ = 81775890.

The previous prime is 81775871. The next prime is 81775901. The reversal of 81775891 is 19857718.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81775891 - 2¹⁹ = 81251603 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81775801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40887945 + 40887946.

It is an arithmetic number, because the mean of its divisors is an integer number (40887946).

Almost surely, 2^81775891 is an apocalyptic number.

81775891 is a deficient number, since it is larger than the sum of its proper divisors (1).

81775891 is an equidigital number, since it uses as much as digits as its factorization.

81775891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141120, while the sum is 46.

The square root of 81775891 is about 9043.0023222379. The cubic root of 81775891 is about 434.0519998996.

The spelling of 81775891 in words is "eighty-one million, seven hundred seventy-five thousand, eight hundred ninety-one".