81820512 has 72 divisors (see below), whose sum is σ = 234614016. Its totient is φ = 27046656.

The previous prime is 81820477. The next prime is 81820549. The reversal of 81820512 is 21502818.

It is a tau number, because it is divible by the number of its divisors (72).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 35458 + ... + 37694.

It is an arithmetic number, because the mean of its divisors is an integer number (3258528).

Almost surely, 2^81820512 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 81820512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117307008).

81820512 is an abundant number, since it is smaller than the sum of its proper divisors (152793504).

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

81820512 is a wasteful number, since it uses less digits than its factorization.

81820512 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2380 (or 2369 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 81820512 is about 9045.4691420622. The cubic root of 81820512 is about 434.1309323430.

The spelling of 81820512 in words is "eighty-one million, eight hundred twenty thousand, five hundred twelve".