81306813 has 16 divisors (see below), whose sum is σ = 126919296. Its totient is φ = 45327360.

The previous prime is 81306811. The next prime is 81306821. The reversal of 81306813 is 31860318.

It is not a de Polignac number, because 81306813 - 2¹ = 81306811 is a prime.

It is a super-2 number, since 2×81306813² = 13221595680433938, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81306811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46356 + ... + 48077.

It is an arithmetic number, because the mean of its divisors is an integer number (7932456).

Almost surely, 2^81306813 is an apocalyptic number.

It is an amenable number.

81306813 is a deficient number, since it is larger than the sum of its proper divisors (45612483).

81306813 is a wasteful number, since it uses less digits than its factorization.

81306813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94484.

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 81306813 is about 9017.0290561803. The cubic root of 81306813 is about 433.2204802111.

The spelling of 81306813 in words is "eighty-one million, three hundred six thousand, eight hundred thirteen".