81709791 has 8 divisors (see below), whose sum is σ = 112703280. Its totient is φ = 52594752.

The previous prime is 81709751. The next prime is 81709799. The reversal of 81709791 is 19790718.

It is a happy number.

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

It is a de Polignac number, because none of the positive numbers 2^k-81709791 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81709799) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 469510 + ... + 469683.

It is an arithmetic number, because the mean of its divisors is an integer number (14087910).

Almost surely, 2^81709791 is an apocalyptic number.

81709791 is a deficient number, since it is larger than the sum of its proper divisors (30993489).

81709791 is a wasteful number, since it uses less digits than its factorization.

81709791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 939225.

The product of its (nonzero) digits is 31752, while the sum is 42.

The square root of 81709791 is about 9039.3468237478. The cubic root of 81709791 is about 433.9350193297.

The spelling of 81709791 in words is "eighty-one million, seven hundred nine thousand, seven hundred ninety-one".