81697709 has 2 divisors, whose sum is σ = 81697710. Its totient is φ = 81697708.

The previous prime is 81697697. The next prime is 81697747. The reversal of 81697709 is 90779618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 58446025 + 23251684 = 7645^2 + 4822^2 .

It is a cyclic number.

It is not a de Polignac number, because 81697709 - 2⁸ = 81697453 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81697799) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40848854 + 40848855.

It is an arithmetic number, because the mean of its divisors is an integer number (40848855).

Almost surely, 2^81697709 is an apocalyptic number.

It is an amenable number.

81697709 is a deficient number, since it is larger than the sum of its proper divisors (1).

81697709 is an equidigital number, since it uses as much as digits as its factorization.

81697709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 190512, while the sum is 47.

The square root of 81697709 is about 9038.6784985417. The cubic root of 81697709 is about 433.9136303739.

The spelling of 81697709 in words is "eighty-one million, six hundred ninety-seven thousand, seven hundred nine".