81539806 has 4 divisors (see below), whose sum is σ = 122309712. Its totient is φ = 40769902.

The previous prime is 81539729. The next prime is 81539813. The reversal of 81539806 is 60893518.

It is a happy number.

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

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 a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20384950 + ... + 20384953.

It is an arithmetic number, because the mean of its divisors is an integer number (30577428).

Almost surely, 2^81539806 is an apocalyptic number.

81539806 is a deficient number, since it is larger than the sum of its proper divisors (40769906).

81539806 is a wasteful number, since it uses less digits than its factorization.

81539806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40769905.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 81539806 is about 9029.9394239386. The cubic root of 81539806 is about 433.6338981171.

The spelling of 81539806 in words is "eighty-one million, five hundred thirty-nine thousand, eight hundred six".