81815850 has 36 divisors (see below), whose sum is σ = 219813126. Its totient is φ = 21817440.

The previous prime is 81815791. The next prime is 81815857. The reversal of 81815850 is 5851818.

It can be written as a sum of positive squares in 3 ways, for example, as 62394201 + 19421649 = 7899^2 + 4407^2 .

It is a super-2 number, since 2×81815850² = 13387666622445000, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81815857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 90457 + ... + 91356.

Almost surely, 2^81815850 is an apocalyptic number.

81815850 is an abundant number, since it is smaller than the sum of its proper divisors (137997276).

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

81815850 is a wasteful number, since it uses less digits than its factorization.

81815850 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 181831 (or 181823 counting only the distinct ones).

The product of its (nonzero) digits is 12800, while the sum is 36.

The square root of 81815850 is about 9045.2114403147. The cubic root of 81815850 is about 434.1226868277.

The spelling of 81815850 in words is "eighty-one million, eight hundred fifteen thousand, eight hundred fifty".