81651856 has 80 divisors (see below), whose sum is σ = 187987968. Its totient is φ = 33868800.

The previous prime is 81651841. The next prime is 81651943. The reversal of 81651856 is 65815618.

It is an unprimeable number.

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, 290436 + ... + 290716.

Almost surely, 2^81651856 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 81651856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93993984).

81651856 is an abundant number, since it is smaller than the sum of its proper divisors (106336112).

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

81651856 is a wasteful number, since it uses less digits than its factorization.

81651856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 440 (or 434 counting only the distinct ones).

The product of its digits is 57600, while the sum is 40.

The square root of 81651856 is about 9036.1416544895. The cubic root of 81651856 is about 433.8324368889.

The spelling of 81651856 in words is "eighty-one million, six hundred fifty-one thousand, eight hundred fifty-six".