172720128 has 128 divisors (see below), whose sum is σ = 528474240. Its totient is φ = 49152000.

The previous prime is 172720123. The next prime is 172720129. The reversal of 172720128 is 821027271.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

It is a junction number, because it is equal to n+sod(n) for n = 172720095 and 172720104.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172720123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 688003 + ... + 688253.

It is an arithmetic number, because the mean of its divisors is an integer number (4128705).

Almost surely, 2^172720128 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 172720128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (264237120).

172720128 is an abundant number, since it is smaller than the sum of its proper divisors (355754112).

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

172720128 is an frugal number, since it uses more digits than its factorization.

172720128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291 (or 263 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 30.

The square root of 172720128 is about 13142.3029945288. The cubic root of 172720128 is about 556.9048289876.

Adding to 172720128 its reverse (821027271), we get a palindrome (993747399).

The spelling of 172720128 in words is "one hundred seventy-two million, seven hundred twenty thousand, one hundred twenty-eight".