81491850 has 144 divisors (see below), whose sum is σ = 242689824. Its totient is φ = 19440000.

The previous prime is 81491833. The next prime is 81491881. The reversal of 81491850 is 5819418.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 499869 + ... + 500031.

It is an arithmetic number, because the mean of its divisors is an integer number (1685346).

Almost surely, 2^81491850 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81491850, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (121344912).

81491850 is an abundant number, since it is smaller than the sum of its proper divisors (161197974).

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

81491850 is a wasteful number, since it uses less digits than its factorization.

81491850 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293 (or 285 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 81491850 is about 9027.2836445965. The cubic root of 81491850 is about 433.5488704218.

It can be divided in two parts, 8149 and 1850, that added together give a palindrome (9999).

The spelling of 81491850 in words is "eighty-one million, four hundred ninety-one thousand, eight hundred fifty".