81163813 has 2 divisors, whose sum is σ = 81163814. Its totient is φ = 81163812.

The previous prime is 81163811. The next prime is 81163853. The reversal of 81163813 is 31836118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80964004 + 199809 = 8998^2 + 447^2 .

It is a cyclic number.

It is not a de Polignac number, because 81163813 - 2¹ = 81163811 is a prime.

Together with 81163811, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81163811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40581906 + 40581907.

It is an arithmetic number, because the mean of its divisors is an integer number (40581907).

Almost surely, 2^81163813 is an apocalyptic number.

It is an amenable number.

81163813 is a deficient number, since it is larger than the sum of its proper divisors (1).

81163813 is an equidigital number, since it uses as much as digits as its factorization.

81163813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3456, while the sum is 31.

The square root of 81163813 is about 9009.0961255833. The cubic root of 81163813 is about 432.9663527449.

The spelling of 81163813 in words is "eighty-one million, one hundred sixty-three thousand, eight hundred thirteen".