81311850 has 120 divisors (see below), whose sum is σ = 239418828. Its totient is φ = 20390400.

The previous prime is 81311837. The next prime is 81311861. The reversal of 81311850 is 5811318.

It can be written as a sum of positive squares in 6 ways, for example, as 60326289 + 20985561 = 7767^2 + 4581^2 .

It is a super-2 number, since 2×81311850² = 13223233900845000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 68260 + ... + 69440.

Almost surely, 2^81311850 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81311850, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119709414).

81311850 is an abundant number, since it is smaller than the sum of its proper divisors (158106978).

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

81311850 is a wasteful number, since it uses less digits than its factorization.

81311850 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1222 (or 1208 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 27.

The square root of 81311850 is about 9017.3083567104. The cubic root of 81311850 is about 433.2294261056.

The spelling of 81311850 in words is "eighty-one million, three hundred eleven thousand, eight hundred fifty".