81371918 has 4 divisors (see below), whose sum is σ = 122057880. Its totient is φ = 40685958.

The previous prime is 81371909. The next prime is 81371929. The reversal of 81371918 is 81917318.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20342978 + ... + 20342981.

It is an arithmetic number, because the mean of its divisors is an integer number (30514470).

Almost surely, 2^81371918 is an apocalyptic number.

81371918 is a deficient number, since it is larger than the sum of its proper divisors (40685962).

81371918 is a wasteful number, since it uses less digits than its factorization.

81371918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40685961.

The product of its digits is 12096, while the sum is 38.

The square root of 81371918 is about 9020.6384474714. The cubic root of 81371918 is about 433.3360805874.

The spelling of 81371918 in words is "eighty-one million, three hundred seventy-one thousand, nine hundred eighteen".