81649218 has 32 divisors (see below), whose sum is σ = 194743296. Its totient is φ = 22313808.

The previous prime is 81649207. The next prime is 81649231. The reversal of 81649218 is 81294618.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41296 + ... + 43227.

It is an arithmetic number, because the mean of its divisors is an integer number (6085728).

Almost surely, 2^81649218 is an apocalyptic number.

81649218 is an abundant number, since it is smaller than the sum of its proper divisors (113094078).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81649218 is a wasteful number, since it uses less digits than its factorization.

81649218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84558.

The product of its digits is 27648, while the sum is 39.

The square root of 81649218 is about 9035.9956839299. The cubic root of 81649218 is about 433.8277647669.

The spelling of 81649218 in words is "eighty-one million, six hundred forty-nine thousand, two hundred eighteen".