81705690 has 48 divisors (see below), whose sum is σ = 231749856.
Its totient is φ = 19807200.
The previous prime is 81705653. The next prime is 81705691. The reversal of 81705690 is 9650718.
It is a super-2 number, since 2×817056902 = 13351639556752200, which contains 22 as substring.
It is not an unprimeable number, because it can be changed into a prime (81705691) 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 23 ways as a sum of consecutive naturals, for example, 40276 + ... + 42255.
It is an arithmetic number, because the mean of its divisors is an integer number (4828122).
Almost surely, 281705690 is an apocalyptic number.
81705690 is an abundant number, since it is smaller than the sum of its proper divisors (150044166).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
81705690 is a wasteful number, since it uses less digits than its factorization.
81705690 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 82555 (or 82552 counting only the distinct ones).
The product of its (nonzero) digits is 15120, while the sum is 36.
The square root of 81705690 is about 9039.1199792900.
The cubic root of 81705690 is about 433.9277595009.
The spelling of 81705690 in words is "eighty-one million, seven hundred five thousand, six hundred ninety".