81191653 has 4 divisors (see below), whose sum is σ = 83386060. Its totient is φ = 78997248.

The previous prime is 81191641. The next prime is 81191681. The reversal of 81191653 is 35619118.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 77739489 + 3452164 = 8817^2 + 1858^2 .

It is a cyclic number.

It is not a de Polignac number, because 81191653 - 2⁹ = 81191141 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81191683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1097148 + ... + 1097221.

It is an arithmetic number, because the mean of its divisors is an integer number (20846515).

Almost surely, 2^81191653 is an apocalyptic number.

It is an amenable number.

81191653 is a deficient number, since it is larger than the sum of its proper divisors (2194407).

81191653 is a wasteful number, since it uses less digits than its factorization.

81191653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2194406.

The product of its digits is 6480, while the sum is 34.

The square root of 81191653 is about 9010.6410981683. The cubic root of 81191653 is about 433.0158510164.

The spelling of 81191653 in words is "eighty-one million, one hundred ninety-one thousand, six hundred fifty-three".