81747706 has 4 divisors (see below), whose sum is σ = 122621562. Its totient is φ = 40873852.

The previous prime is 81747691. The next prime is 81747737. The reversal of 81747706 is 60774718.

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., 81270225 + 477481 = 9015^2 + 691^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20436925 + ... + 20436928.

Almost surely, 2^81747706 is an apocalyptic number.

81747706 is a deficient number, since it is larger than the sum of its proper divisors (40873856).

81747706 is a wasteful number, since it uses less digits than its factorization.

81747706 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40873855.

The product of its (nonzero) digits is 65856, while the sum is 40.

The square root of 81747706 is about 9041.4438006327. The cubic root of 81747706 is about 434.0021271672.

The spelling of 81747706 in words is "eighty-one million, seven hundred forty-seven thousand, seven hundred six".