81806218 has 8 divisors (see below), whose sum is σ = 132148548. Its totient is φ = 37756704.

The previous prime is 81806203. The next prime is 81806251. The reversal of 81806218 is 81260818.

It can be written as a sum of positive squares in 2 ways, for example, as 76685049 + 5121169 = 8757^2 + 2263^2 .

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, 1573171 + ... + 1573222.

Almost surely, 2^81806218 is an apocalyptic number.

81806218 is a deficient number, since it is larger than the sum of its proper divisors (50342330).

81806218 is a wasteful number, since it uses less digits than its factorization.

81806218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3146408.

The product of its (nonzero) digits is 6144, while the sum is 34.

The square root of 81806218 is about 9044.6789882229. The cubic root of 81806218 is about 434.1056500562.

The spelling of 81806218 in words is "eighty-one million, eight hundred six thousand, two hundred eighteen".