181721664 has 112 divisors (see below), whose sum is σ = 539943040. Its totient is φ = 59927040.

The previous prime is 181721641. The next prime is 181721671. The reversal of 181721664 is 466127181.

It is a happy number.

181721664 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (36).

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, 177474 + ... + 178494.

It is an arithmetic number, because the mean of its divisors is an integer number (4820920).

Almost surely, 2^181721664 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 181721664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (269971520).

181721664 is an abundant number, since it is smaller than the sum of its proper divisors (358221376).

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

181721664 is a wasteful number, since it uses less digits than its factorization.

181721664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1145 (or 1129 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 181721664 is about 13480.4177976797. The cubic root of 181721664 is about 566.4160725115.

The spelling of 181721664 in words is "one hundred eighty-one million, seven hundred twenty-one thousand, six hundred sixty-four".