81851000 has 128 divisors (see below), whose sum is σ = 239016960. Its totient is φ = 25488000.

The previous prime is 81850999. The next prime is 81851083. The reversal of 81851000 is 15818.

It is a congruent number.

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 31 ways as a sum of consecutive naturals, for example, 76469 + ... + 77531.

It is an arithmetic number, because the mean of its divisors is an integer number (1867320).

Almost surely, 2^81851000 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81851000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119508480).

81851000 is an abundant number, since it is smaller than the sum of its proper divisors (157165960).

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

81851000 is a wasteful number, since it uses less digits than its factorization.

81851000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1102 (or 1088 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 23.

The square root of 81851000 is about 9047.1542487127. The cubic root of 81851000 is about 434.1848476751.

Adding to 81851000 its reverse (15818), we get a palindrome (81866818).

The spelling of 81851000 in words is "eighty-one million, eight hundred fifty-one thousand".