81723391 has 8 divisors (see below), whose sum is σ = 82298880. Its totient is φ = 81150552.

The previous prime is 81723359. The next prime is 81723401. The reversal of 81723391 is 19332718.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81723391 - 2⁵ = 81723359 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81723331) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 144876 + ... + 145438.

It is an arithmetic number, because the mean of its divisors is an integer number (10287360).

Almost surely, 2^81723391 is an apocalyptic number.

81723391 is a deficient number, since it is larger than the sum of its proper divisors (575489).

81723391 is a wasteful number, since it uses less digits than its factorization.

81723391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1325.

The product of its digits is 9072, while the sum is 34.

The square root of 81723391 is about 9040.0990591918. The cubic root of 81723391 is about 433.9590931027.

The spelling of 81723391 in words is "eighty-one million, seven hundred twenty-three thousand, three hundred ninety-one".