81818197 has 2 divisors, whose sum is σ = 81818198. Its totient is φ = 81818196.

The previous prime is 81818179. The next prime is 81818227. The reversal of 81818197 is 79181818.

Together with previous prime (81818179) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 67141636 + 14676561 = 8194^2 + 3831^2 .

It is a cyclic number.

It is not a de Polignac number, because 81818197 - 2⁷ = 81818069 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81818147) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40909098 + 40909099.

It is an arithmetic number, because the mean of its divisors is an integer number (40909099).

Almost surely, 2^81818197 is an apocalyptic number.

It is an amenable number.

81818197 is a deficient number, since it is larger than the sum of its proper divisors (1).

81818197 is an equidigital number, since it uses as much as digits as its factorization.

81818197 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32256, while the sum is 43.

The square root of 81818197 is about 9045.3411765394. The cubic root of 81818197 is about 434.1268379232.

The spelling of 81818197 in words is "eighty-one million, eight hundred eighteen thousand, one hundred ninety-seven".