81189197 has 2 divisors, whose sum is σ = 81189198. Its totient is φ = 81189196.

The previous prime is 81189187. The next prime is 81189239. The reversal of 81189197 is 79198118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 70073641 + 11115556 = 8371^2 + 3334^2 .

It is a cyclic number.

It is not a de Polignac number, because 81189197 - 2⁴ = 81189181 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81189107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40594598 + 40594599.

It is an arithmetic number, because the mean of its divisors is an integer number (40594599).

Almost surely, 2^81189197 is an apocalyptic number.

It is an amenable number.

81189197 is a deficient number, since it is larger than the sum of its proper divisors (1).

81189197 is an equidigital number, since it uses as much as digits as its factorization.

81189197 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 44.

The square root of 81189197 is about 9010.5048138270. The cubic root of 81189197 is about 433.0114848136.

The spelling of 81189197 in words is "eighty-one million, one hundred eighty-nine thousand, one hundred ninety-seven".