81911648 has 96 divisors (see below), whose sum is σ = 207277056. Its totient is φ = 30970368.

The previous prime is 81911633. The next prime is 81911681. The reversal of 81911648 is 84611918.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 66365 + ... + 67587.

It is an arithmetic number, because the mean of its divisors is an integer number (2159136).

Almost surely, 2^81911648 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 81911648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103638528).

81911648 is an abundant number, since it is smaller than the sum of its proper divisors (125365408).

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

81911648 is a wasteful number, since it uses less digits than its factorization.

81911648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1276 (or 1268 counting only the distinct ones).

The product of its digits is 13824, while the sum is 38.

The square root of 81911648 is about 9050.5054002525. The cubic root of 81911648 is about 434.2920585078.

The spelling of 81911648 in words is "eighty-one million, nine hundred eleven thousand, six hundred forty-eight".