81767866 has 4 divisors (see below), whose sum is σ = 122651802. Its totient is φ = 40883932.

The previous prime is 81767857. The next prime is 81767867. The reversal of 81767866 is 66876718.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 66876718 = 2 ⋅33438359.

It can be written as a sum of positive squares in only one way, i.e., 81522841 + 245025 = 9029^2 + 495^2 .

It is not an unprimeable number, because it can be changed into a prime (81767867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20441965 + ... + 20441968.

Almost surely, 2^81767866 is an apocalyptic number.

81767866 is a deficient number, since it is larger than the sum of its proper divisors (40883936).

81767866 is a wasteful number, since it uses less digits than its factorization.

81767866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40883935.

The product of its digits is 677376, while the sum is 49.

The square root of 81767866 is about 9042.5585980960. The cubic root of 81767866 is about 434.0378010071.

The spelling of 81767866 in words is "eighty-one million, seven hundred sixty-seven thousand, eight hundred sixty-six".