81911887 has 2 divisors, whose sum is σ = 81911888. Its totient is φ = 81911886.

The previous prime is 81911881. The next prime is 81911903. The reversal of 81911887 is 78811918.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81911887 - 2⁷ = 81911759 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81911881) 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, 40955943 + 40955944.

It is an arithmetic number, because the mean of its divisors is an integer number (40955944).

Almost surely, 2^81911887 is an apocalyptic number.

81911887 is a deficient number, since it is larger than the sum of its proper divisors (1).

81911887 is an equidigital number, since it uses as much as digits as its factorization.

81911887 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32256, while the sum is 43.

The square root of 81911887 is about 9050.5186039254. The cubic root of 81911887 is about 434.2924808966.

The spelling of 81911887 in words is "eighty-one million, nine hundred eleven thousand, eight hundred eighty-seven".