81959643 has 6 divisors (see below), whose sum is σ = 118386164. Its totient is φ = 54639756.

The previous prime is 81959639. The next prime is 81959659. The reversal of 81959643 is 34695918.

It is a happy number.

81959643 is a `hidden beast` number, since 8 + 19 + 596 + 43 = 666.

It is not a de Polignac number, because 81959643 - 2² = 81959639 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81959623) 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, 4553305 + ... + 4553322.

Almost surely, 2^81959643 is an apocalyptic number.

81959643 is a deficient number, since it is larger than the sum of its proper divisors (36426521).

81959643 is a wasteful number, since it uses less digits than its factorization.

81959643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9106633 (or 9106630 counting only the distinct ones).

The product of its digits is 233280, while the sum is 45.

The square root of 81959643 is about 9053.1565213466. The cubic root of 81959643 is about 434.3768644262.

The spelling of 81959643 in words is "eighty-one million, nine hundred fifty-nine thousand, six hundred forty-three".