81787216 has 40 divisors (see below), whose sum is σ = 184184640. Its totient is φ = 34454784.

The previous prime is 81787193. The next prime is 81787217. The reversal of 81787216 is 61278718.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81787217) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 420 + ... + 12796.

It is an arithmetic number, because the mean of its divisors is an integer number (4604616).

Almost surely, 2^81787216 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 81787216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (92092320).

81787216 is an abundant number, since it is smaller than the sum of its proper divisors (102397424).

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

81787216 is a wasteful number, since it uses less digits than its factorization.

81787216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12451 (or 12445 counting only the distinct ones).

The product of its digits is 37632, while the sum is 40.

The square root of 81787216 is about 9043.6284753411. The cubic root of 81787216 is about 434.0720360086.

The spelling of 81787216 in words is "eighty-one million, seven hundred eighty-seven thousand, two hundred sixteen".