81705601 has 4 divisors (see below), whose sum is σ = 81733972.
Its totient is φ = 81677232.
The previous prime is 81705571. The next prime is 81705623. The reversal of 81705601 is 10650718.
It is a happy number.
It is a semiprime because it is the product of two primes.
It can be written as a sum of positive squares in 2 ways, for example, as 70308225 + 11397376 = 8385^2 + 3376^2
It is a cyclic number.
It is not a de Polignac number, because 81705601 - 27 = 81705473 is a prime.
It is a Duffinian number.
It is a self number, because there is not a number n which added to its sum of digits gives 81705601.
It is not an unprimeable number, because it can be changed into a prime (81705691) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9306 + ... + 15811.
It is an arithmetic number, because the mean of its divisors is an integer number (20433493).
It is a 2880-hyperperfect number.
Almost surely, 281705601 is an apocalyptic number.
It is an amenable number.
81705601 is a deficient number, since it is larger than the sum of its proper divisors (28371).
81705601 is a wasteful number, since it uses less digits than its factorization.
81705601 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 28370.
The product of its (nonzero) digits is 1680, while the sum is 28.
The square root of 81705601 is about 9039.1150562431.
The cubic root of 81705601 is about 433.9276019452.
The spelling of 81705601 in words is "eighty-one million, seven hundred five thousand, six hundred one".