81911766 has 16 divisors (see below), whose sum is σ = 164187504. Its totient is φ = 27243264.

The previous prime is 81911761. The next prime is 81911771. The reversal of 81911766 is 66711918.

It is an interprime number because it is at equal distance from previous prime (81911761) and next prime (81911771).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81911761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12195 + ... + 17678.

It is an arithmetic number, because the mean of its divisors is an integer number (10261719).

Almost surely, 2^81911766 is an apocalyptic number.

81911766 is an abundant number, since it is smaller than the sum of its proper divisors (82275738).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81911766 is a wasteful number, since it uses less digits than its factorization.

81911766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30335.

The product of its digits is 18144, while the sum is 39.

The square root of 81911766 is about 9050.5119192231. The cubic root of 81911766 is about 434.2922670513.

The spelling of 81911766 in words is "eighty-one million, nine hundred eleven thousand, seven hundred sixty-six".