81166813 has 12 divisors (see below), whose sum is σ = 100447968. Its totient is φ = 64218960.

The previous prime is 81166807. The next prime is 81166819. The reversal of 81166813 is 31866118.

It is an interprime number because it is at equal distance from previous prime (81166807) and next prime (81166819).

It is not a de Polignac number, because 81166813 - 2¹³ = 81158621 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81166819) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 33123 + ... + 35488.

It is an arithmetic number, because the mean of its divisors is an integer number (8370664).

Almost surely, 2^81166813 is an apocalyptic number.

It is an amenable number.

81166813 is a deficient number, since it is larger than the sum of its proper divisors (19281155).

81166813 is a wasteful number, since it uses less digits than its factorization.

81166813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68644 (or 68631 counting only the distinct ones).

The product of its digits is 6912, while the sum is 34.

The square root of 81166813 is about 9009.2626224348. The cubic root of 81166813 is about 432.9716871545.

The spelling of 81166813 in words is "eighty-one million, one hundred sixty-six thousand, eight hundred thirteen".