81090109 has 2 divisors, whose sum is σ = 81090110. Its totient is φ = 81090108.

The previous prime is 81090091. The next prime is 81090127. The reversal of 81090109 is 90109018.

Together with previous prime (81090091) it forms an Ormiston pair, because they use the same digits, order apart.

It is a balanced prime because it is at equal distance from previous prime (81090091) and next prime (81090127).

It can be written as a sum of positive squares in only one way, i.e., 81054009 + 36100 = 9003^2 + 190^2 .

It is a cyclic number.

It is not a de Polignac number, because 81090109 - 2⁵ = 81090077 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81090509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40545054 + 40545055.

It is an arithmetic number, because the mean of its divisors is an integer number (40545055).

Almost surely, 2^81090109 is an apocalyptic number.

It is an amenable number.

81090109 is a deficient number, since it is larger than the sum of its proper divisors (1).

81090109 is an equidigital number, since it uses as much as digits as its factorization.

81090109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 28.

The square root of 81090109 is about 9005.0046640743. The cubic root of 81090109 is about 432.8352556660.

The spelling of 81090109 in words is "eighty-one million, ninety thousand, one hundred nine".