81820117 has 2 divisors, whose sum is σ = 81820118. Its totient is φ = 81820116.

The previous prime is 81820073. The next prime is 81820121. The reversal of 81820117 is 71102818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 76842756 + 4977361 = 8766^2 + 2231^2 .

It is a cyclic number.

It is not a de Polignac number, because 81820117 - 2¹¹ = 81818069 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81820217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40910058 + 40910059.

It is an arithmetic number, because the mean of its divisors is an integer number (40910059).

Almost surely, 2^81820117 is an apocalyptic number.

It is an amenable number.

81820117 is a deficient number, since it is larger than the sum of its proper divisors (1).

81820117 is an equidigital number, since it uses as much as digits as its factorization.

81820117 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 81820117 is about 9045.4473079003. The cubic root of 81820117 is about 434.1302337326.

The spelling of 81820117 in words is "eighty-one million, eight hundred twenty thousand, one hundred seventeen".