81518642 has 4 divisors (see below), whose sum is σ = 122277966. Its totient is φ = 40759320.

The previous prime is 81518641. The next prime is 81518653. The reversal of 81518642 is 24681518.

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., 78659161 + 2859481 = 8869^2 + 1691^2 .

It is not an unprimeable number, because it can be changed into a prime (81518641) by changing a digit.

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, 20379659 + ... + 20379662.

Almost surely, 2^81518642 is an apocalyptic number.

81518642 is a deficient number, since it is larger than the sum of its proper divisors (40759324).

81518642 is a wasteful number, since it uses less digits than its factorization.

81518642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40759323.

The product of its digits is 15360, while the sum is 35.

The square root of 81518642 is about 9028.7674684865. The cubic root of 81518642 is about 433.5963777027.

The spelling of 81518642 in words is "eighty-one million, five hundred eighteen thousand, six hundred forty-two".