81657216 has 96 divisors (see below), whose sum is σ = 238441320. Its totient is φ = 26818560.

The previous prime is 81657209. The next prime is 81657287. The reversal of 81657216 is 61275618.

81657216 is a `hidden beast` number, since 81 + 6 + 572 + 1 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (96).

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 11 ways as a sum of consecutive naturals, for example, 83611 + ... + 84581.

Almost surely, 2^81657216 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 81657216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119220660).

81657216 is an abundant number, since it is smaller than the sum of its proper divisors (156784104).

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

81657216 is a wasteful number, since it uses less digits than its factorization.

81657216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1064 (or 1049 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 81657216 is about 9036.4382363850. The cubic root of 81657216 is about 433.8419295940.

The spelling of 81657216 in words is "eighty-one million, six hundred fifty-seven thousand, two hundred sixteen".