81689216 has 128 divisors (see below), whose sum is σ = 204456960. Its totient is φ = 31703040.

The previous prime is 81689213. The next prime is 81689269. The reversal of 81689216 is 61298618.

It is a tau number, because it is divible by the number of its divisors (128).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81689213) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 472106 + ... + 472278.

It is an arithmetic number, because the mean of its divisors is an integer number (1597320).

Almost surely, 2^81689216 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 81689216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (102228480).

81689216 is an abundant number, since it is smaller than the sum of its proper divisors (122767744).

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

81689216 is a wasteful number, since it uses less digits than its factorization.

81689216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242 (or 230 counting only the distinct ones).

The product of its digits is 41472, while the sum is 41.

The square root of 81689216 is about 9038.2086720766. The cubic root of 81689216 is about 433.8985938193.

The spelling of 81689216 in words is "eighty-one million, six hundred eighty-nine thousand, two hundred sixteen".