81706642 has 4 divisors (see below), whose sum is σ = 122559966. Its totient is φ = 40853320.

The previous prime is 81706627. The next prime is 81706643. The reversal of 81706642 is 24660718.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 51136801 + 30569841 = 7151^2 + 5529^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81706598 and 81706607.

It is not an unprimeable number, because it can be changed into a prime (81706643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20426659 + ... + 20426662.

Almost surely, 2^81706642 is an apocalyptic number.

81706642 is a deficient number, since it is larger than the sum of its proper divisors (40853324).

81706642 is a wasteful number, since it uses less digits than its factorization.

81706642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40853323.

The product of its (nonzero) digits is 16128, while the sum is 34.

The square root of 81706642 is about 9039.1726391302. The cubic root of 81706642 is about 433.9294448083.

The spelling of 81706642 in words is "eighty-one million, seven hundred six thousand, six hundred forty-two".