81729371 has 4 divisors (see below), whose sum is σ = 82764000. Its totient is φ = 80694744.

The previous prime is 81729343. The next prime is 81729377. The reversal of 81729371 is 17392718.

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

It is a cyclic number.

It is not a de Polignac number, because 81729371 - 2¹⁸ = 81467227 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81729377) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 517196 + ... + 517353.

It is an arithmetic number, because the mean of its divisors is an integer number (20691000).

Almost surely, 2^81729371 is an apocalyptic number.

81729371 is a deficient number, since it is larger than the sum of its proper divisors (1034629).

81729371 is a wasteful number, since it uses less digits than its factorization.

81729371 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1034628.

The product of its digits is 21168, while the sum is 38.

The square root of 81729371 is about 9040.4298017296. The cubic root of 81729371 is about 433.9696776369.

The spelling of 81729371 in words is "eighty-one million, seven hundred twenty-nine thousand, three hundred seventy-one".