81868691 has 2 divisors, whose sum is σ = 81868692. Its totient is φ = 81868690.

The previous prime is 81868673. The next prime is 81868741. The reversal of 81868691 is 19686818.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81868691 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81868601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40934345 + 40934346.

It is an arithmetic number, because the mean of its divisors is an integer number (40934346).

Almost surely, 2^81868691 is an apocalyptic number.

81868691 is a deficient number, since it is larger than the sum of its proper divisors (1).

81868691 is an equidigital number, since it uses as much as digits as its factorization.

81868691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 165888, while the sum is 47.

The square root of 81868691 is about 9048.1319066424. The cubic root of 81868691 is about 434.2161265062.

The spelling of 81868691 in words is "eighty-one million, eight hundred sixty-eight thousand, six hundred ninety-one".