81312018 has 16 divisors (see below), whose sum is σ = 162712800. Its totient is φ = 27089216.

The previous prime is 81312013. The next prime is 81312031. The reversal of 81312018 is 81021318.

It is a super-2 number, since 2×81312018² = 13223288542464648, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81312013) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18058 + ... + 22106.

It is an arithmetic number, because the mean of its divisors is an integer number (10169550).

Almost surely, 2^81312018 is an apocalyptic number.

81312018 is an abundant number, since it is smaller than the sum of its proper divisors (81400782).

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

81312018 is a wasteful number, since it uses less digits than its factorization.

81312018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7401.

The product of its (nonzero) digits is 384, while the sum is 24.

The square root of 81312018 is about 9017.3176721240. The cubic root of 81312018 is about 433.2297244733.

The spelling of 81312018 in words is "eighty-one million, three hundred twelve thousand, eighteen".