81475109 has 2 divisors, whose sum is σ = 81475110. Its totient is φ = 81475108.

The previous prime is 81475087. The next prime is 81475117. The reversal of 81475109 is 90157418.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72624484 + 8850625 = 8522^2 + 2975^2 .

It is a cyclic number.

It is not a de Polignac number, because 81475109 - 2⁸ = 81474853 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81475129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40737554 + 40737555.

It is an arithmetic number, because the mean of its divisors is an integer number (40737555).

Almost surely, 2^81475109 is an apocalyptic number.

It is an amenable number.

81475109 is a deficient number, since it is larger than the sum of its proper divisors (1).

81475109 is an equidigital number, since it uses as much as digits as its factorization.

81475109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10080, while the sum is 35.

The square root of 81475109 is about 9026.3563523716. The cubic root of 81475109 is about 433.5191801779.

The spelling of 81475109 in words is "eighty-one million, four hundred seventy-five thousand, one hundred nine".