81978218 has 8 divisors (see below), whose sum is σ = 140534112. Its totient is φ = 35133516.

The previous prime is 81978209. The next prime is 81978251. The reversal of 81978218 is 81287918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2927780 + ... + 2927807.

It is an arithmetic number, because the mean of its divisors is an integer number (17566764).

Almost surely, 2^81978218 is an apocalyptic number.

81978218 is a deficient number, since it is larger than the sum of its proper divisors (58555894).

81978218 is a wasteful number, since it uses less digits than its factorization.

81978218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5855596.

The product of its digits is 64512, while the sum is 44.

The square root of 81978218 is about 9054.1823485061. The cubic root of 81978218 is about 434.4096770825.

The spelling of 81978218 in words is "eighty-one million, nine hundred seventy-eight thousand, two hundred eighteen".