165611721600 has 1152 divisors, whose sum is σ = 692422348800. Its totient is φ = 37324800000.

The previous prime is 165611721497. The next prime is 165611721661. The reversal of 165611721600 is 6127116561.

It is a happy number.

165611721600 is a `hidden beast` number, since 1 + 6 + 561 + 17 + 21 + 60 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (1152).

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 pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 220521225 + ... + 220521975.

Almost surely, 2^165611721600 is an apocalyptic number.

165611721600 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 165611721600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (346211174400).

165611721600 is an abundant number, since it is smaller than the sum of its proper divisors (526810627200).

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

165611721600 is a wasteful number, since it uses less digits than its factorization.

165611721600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844 (or 824 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 36.

The spelling of 165611721600 in words is "one hundred sixty-five billion, six hundred eleven million, seven hundred twenty-one thousand, six hundred".