81686619 has 12 divisors (see below), whose sum is σ = 134847856. Its totient is φ = 46678032.

The previous prime is 81686617. The next prime is 81686651. The reversal of 81686619 is 91668618.

It is a happy number.

It is not a de Polignac number, because 81686619 - 2¹ = 81686617 is a prime.

It is a super-2 number, since 2×81686619² = 13345407447302322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81686617) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 648244 + ... + 648369.

Almost surely, 2^81686619 is an apocalyptic number.

81686619 is a deficient number, since it is larger than the sum of its proper divisors (53161237).

81686619 is a wasteful number, since it uses less digits than its factorization.

81686619 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1296626 (or 1296623 counting only the distinct ones).

The product of its digits is 124416, while the sum is 45.

The square root of 81686619 is about 9038.0650030856. The cubic root of 81686619 is about 433.8939957151.

The spelling of 81686619 in words is "eighty-one million, six hundred eighty-six thousand, six hundred nineteen".