81851790 has 64 divisors (see below), whose sum is σ = 203233536. Its totient is φ = 21084672.

The previous prime is 81851789. The next prime is 81851827. The reversal of 81851790 is 9715818.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 137734 + ... + 138326.

It is an arithmetic number, because the mean of its divisors is an integer number (3175524).

Almost surely, 2^81851790 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81851790, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (101616768).

81851790 is an abundant number, since it is smaller than the sum of its proper divisors (121381746).

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

81851790 is a wasteful number, since it uses less digits than its factorization.

81851790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 753.

The product of its (nonzero) digits is 20160, while the sum is 39.

The square root of 81851790 is about 9047.1979087450. The cubic root of 81851790 is about 434.1862445423.

The spelling of 81851790 in words is "eighty-one million, eight hundred fifty-one thousand, seven hundred ninety".