81705279 has 8 divisors (see below), whose sum is σ = 108982192. Its totient is φ = 54449280.

The previous prime is 81705271. The next prime is 81705329. The reversal of 81705279 is 97250718.

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

It is not a de Polignac number, because 81705279 - 2³ = 81705271 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 (81705271) 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, 12039 + ... + 17559.

It is an arithmetic number, because the mean of its divisors is an integer number (13622774).

Almost surely, 2^81705279 is an apocalyptic number.

81705279 is a deficient number, since it is larger than the sum of its proper divisors (27276913).

81705279 is a wasteful number, since it uses less digits than its factorization.

81705279 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10457.

The product of its (nonzero) digits is 35280, while the sum is 39.

The square root of 81705279 is about 9039.0972447474. The cubic root of 81705279 is about 433.9270319114.

The spelling of 81705279 in words is "eighty-one million, seven hundred five thousand, two hundred seventy-nine".