81705140 has 24 divisors (see below), whose sum is σ = 187179552. Its totient is φ = 29710880.

The previous prime is 81705133. The next prime is 81705157. The reversal of 81705140 is 4150718.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 185474 + ... + 185913.

It is an arithmetic number, because the mean of its divisors is an integer number (7799148).

Almost surely, 2^81705140 is an apocalyptic number.

It is an amenable number.

81705140 is an abundant number, since it is smaller than the sum of its proper divisors (105474412).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81705140 is a wasteful number, since it uses less digits than its factorization.

81705140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 371407 (or 371405 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 81705140 is about 9039.0895559232. The cubic root of 81705140 is about 433.9267858404.

Adding to 81705140 its reverse (4150718), we get a palindrome (85855858).

The spelling of 81705140 in words is "eighty-one million, seven hundred five thousand, one hundred forty".