81786818 has 4 divisors (see below), whose sum is σ = 122680230. Its totient is φ = 40893408.

The previous prime is 81786799. The next prime is 81786821. The reversal of 81786818 is 81868718.

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., 54715609 + 27071209 = 7397^2 + 5203^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20446703 + ... + 20446706.

Almost surely, 2^81786818 is an apocalyptic number.

81786818 is a deficient number, since it is larger than the sum of its proper divisors (40893412).

81786818 is a wasteful number, since it uses less digits than its factorization.

81786818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40893411.

The product of its digits is 172032, while the sum is 47.

The square root of 81786818 is about 9043.6064708721. The cubic root of 81786818 is about 434.0713319012.

The spelling of 81786818 in words is "eighty-one million, seven hundred eighty-six thousand, eight hundred eighteen".