81665797 has 2 divisors, whose sum is σ = 81665798. Its totient is φ = 81665796.

The previous prime is 81665767. The next prime is 81665851. The reversal of 81665797 is 79756618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78393316 + 3272481 = 8854^2 + 1809^2 .

It is a cyclic number.

It is not a de Polignac number, because 81665797 - 2¹¹ = 81663749 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81665797.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81665737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40832898 + 40832899.

It is an arithmetic number, because the mean of its divisors is an integer number (40832899).

Almost surely, 2^81665797 is an apocalyptic number.

It is an amenable number.

81665797 is a deficient number, since it is larger than the sum of its proper divisors (1).

81665797 is an equidigital number, since it uses as much as digits as its factorization.

81665797 is an evil number, because the sum of its binary digits is even.

The product of its digits is 635040, while the sum is 49.

The square root of 81665797 is about 9036.9130238152. The cubic root of 81665797 is about 433.8571259126.

The spelling of 81665797 in words is "eighty-one million, six hundred sixty-five thousand, seven hundred ninety-seven".