81391653 has 12 divisors (see below), whose sum is σ = 134360928. Its totient is φ = 46509480.

The previous prime is 81391619. The next prime is 81391669. The reversal of 81391653 is 35619318.

It is a happy number.

It is not a de Polignac number, because 81391653 - 2⁸ = 81391397 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81391693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 645903 + ... + 646028.

It is an arithmetic number, because the mean of its divisors is an integer number (11196744).

Almost surely, 2^81391653 is an apocalyptic number.

It is an amenable number.

81391653 is a deficient number, since it is larger than the sum of its proper divisors (52969275).

81391653 is a wasteful number, since it uses less digits than its factorization.

81391653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1291944 (or 1291941 counting only the distinct ones).

The product of its digits is 19440, while the sum is 36.

The square root of 81391653 is about 9021.7322616003. The cubic root of 81391653 is about 433.3711098559.

The spelling of 81391653 in words is "eighty-one million, three hundred ninety-one thousand, six hundred fifty-three".