81553500 has 192 divisors, whose sum is σ = 301916160. Its totient is φ = 18619200.

The previous prime is 81553489. The next prime is 81553531. The reversal of 81553500 is 535518.

81553500 is a `hidden beast` number, since 8 + 155 + 3 + 500 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

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 63 ways as a sum of consecutive naturals, for example, 94069 + ... + 94931.

It is an arithmetic number, because the mean of its divisors is an integer number (1572480).

Almost surely, 2^81553500 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 81553500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (150958080).

81553500 is an abundant number, since it is smaller than the sum of its proper divisors (220362660).

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

81553500 is a wasteful number, since it uses less digits than its factorization.

81553500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 898 (or 880 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 27.

The square root of 81553500 is about 9030.6976474689. The cubic root of 81553500 is about 433.6581719473.

The spelling of 81553500 in words is "eighty-one million, five hundred fifty-three thousand, five hundred".