81845820 has 144 divisors (see below), whose sum is σ = 300500928. Its totient is φ = 17602560.

The previous prime is 81845809. The next prime is 81845831. The reversal of 81845820 is 2854818.

It is an interprime number because it is at equal distance from previous prime (81845809) and next prime (81845831).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 19510 + ... + 23330.

It is an arithmetic number, because the mean of its divisors is an integer number (2086812).

Almost surely, 2^81845820 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 81845820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (150250464).

81845820 is an abundant number, since it is smaller than the sum of its proper divisors (218655108).

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

81845820 is a wasteful number, since it uses less digits than its factorization.

81845820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3860 (or 3855 counting only the distinct ones).

The product of its (nonzero) digits is 20480, while the sum is 36.

The square root of 81845820 is about 9046.8679663185. The cubic root of 81845820 is about 434.1756882474.

The spelling of 81845820 in words is "eighty-one million, eight hundred forty-five thousand, eight hundred twenty".