81647793 has 6 divisors (see below), whose sum is σ = 117935714. Its totient is φ = 54431856.

The previous prime is 81647777. The next prime is 81647827. The reversal of 81647793 is 39774618.

It can be written as a sum of positive squares in only one way, i.e., 81216144 + 431649 = 9012^2 + 657^2 .

It is not a de Polignac number, because 81647793 - 2⁴ = 81647777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81647773) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4535980 + ... + 4535997.

Almost surely, 2^81647793 is an apocalyptic number.

It is an amenable number.

81647793 is a deficient number, since it is larger than the sum of its proper divisors (36287921).

81647793 is a wasteful number, since it uses less digits than its factorization.

81647793 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9071983 (or 9071980 counting only the distinct ones).

The product of its digits is 254016, while the sum is 45.

The square root of 81647793 is about 9035.9168322866. The cubic root of 81647793 is about 433.8252409291.

The spelling of 81647793 in words is "eighty-one million, six hundred forty-seven thousand, seven hundred ninety-three".