81605888 has 144 divisors (see below), whose sum is σ = 208782336. Its totient is φ = 30965760.

The previous prime is 81605869. The next prime is 81605891. The reversal of 81605888 is 88850618.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 722120 + ... + 722232.

Almost surely, 2^81605888 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 81605888, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (104391168).

81605888 is an abundant number, since it is smaller than the sum of its proper divisors (127176448).

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

81605888 is a wasteful number, since it uses less digits than its factorization.

81605888 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180 (or 166 counting only the distinct ones).

The product of its (nonzero) digits is 122880, while the sum is 44.

The square root of 81605888 is about 9033.5977329080. The cubic root of 81605888 is about 433.7510092522.

The spelling of 81605888 in words is "eighty-one million, six hundred five thousand, eight hundred eighty-eight".