81686617 has 2 divisors, whose sum is σ = 81686618. Its totient is φ = 81686616.

The previous prime is 81686609. The next prime is 81686651. The reversal of 81686617 is 71668618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 72948681 + 8737936 = 8541^2 + 2956^2 .

It is a cyclic number.

It is not a de Polignac number, because 81686617 - 2³ = 81686609 is a prime.

It is not a weakly prime, because it can be changed into another prime (81686687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40843308 + 40843309.

It is an arithmetic number, because the mean of its divisors is an integer number (40843309).

Almost surely, 2^81686617 is an apocalyptic number.

It is an amenable number.

81686617 is a deficient number, since it is larger than the sum of its proper divisors (1).

81686617 is an equidigital number, since it uses as much as digits as its factorization.

81686617 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96768, while the sum is 43.

The square root of 81686617 is about 9038.0648924424. The cubic root of 81686617 is about 433.8939921740.

The spelling of 81686617 in words is "eighty-one million, six hundred eighty-six thousand, six hundred seventeen".