81911761 has 2 divisors, whose sum is σ = 81911762. Its totient is φ = 81911760.

The previous prime is 81911759. The next prime is 81911771. The reversal of 81911761 is 16711918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 46580625 + 35331136 = 6825^2 + 5944^2 .

It is a cyclic number.

It is not a de Polignac number, because 81911761 - 2¹ = 81911759 is a prime.

It is a super-2 number, since 2×81911761² = 13419073180242242, which contains 22 as substring.

Together with 81911759, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81911701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40955880 + 40955881.

It is an arithmetic number, because the mean of its divisors is an integer number (40955881).

Almost surely, 2^81911761 is an apocalyptic number.

It is an amenable number.

81911761 is a deficient number, since it is larger than the sum of its proper divisors (1).

81911761 is an equidigital number, since it uses as much as digits as its factorization.

81911761 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 34.

The square root of 81911761 is about 9050.5116429957. The cubic root of 81911761 is about 434.2922582147.

The spelling of 81911761 in words is "eighty-one million, nine hundred eleven thousand, seven hundred sixty-one".