81806479 has 4 divisors (see below), whose sum is σ = 82085976. Its totient is φ = 81526984.

The previous prime is 81806467. The next prime is 81806537. The reversal of 81806479 is 97460818.

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

It is a cyclic number.

It is not a de Polignac number, because 81806479 - 2⁵ = 81806447 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81806579) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 139309 + ... + 139894.

It is an arithmetic number, because the mean of its divisors is an integer number (20521494).

Almost surely, 2^81806479 is an apocalyptic number.

81806479 is a deficient number, since it is larger than the sum of its proper divisors (279497).

81806479 is a wasteful number, since it uses less digits than its factorization.

81806479 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 279496.

The product of its (nonzero) digits is 96768, while the sum is 43.

The square root of 81806479 is about 9044.6934165841. The cubic root of 81806479 is about 434.1061117223.

The spelling of 81806479 in words is "eighty-one million, eight hundred six thousand, four hundred seventy-nine".