172728991 has 4 divisors (see below), whose sum is σ = 172756872. Its totient is φ = 172701112.

The previous prime is 172728977. The next prime is 172729001. The reversal of 172728991 is 199827271.

172728991 is a nontrivial binomial coefficient, being equal to C(18587, 2).

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 172728991 - 2²³ = 164340383 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172728911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1 + ... + 18586.

It is an arithmetic number, because the mean of its divisors is an integer number (43189218).

Almost surely, 2^172728991 is an apocalyptic number.

172728991 is the 18586-th triangular number.

172728991 is the 6196-th centered nonagonal number.

172728991 is a deficient number, since it is larger than the sum of its proper divisors (27881).

172728991 is an equidigital number, since it uses as much as digits as its factorization.

172728991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27880.

The product of its digits is 127008, while the sum is 46.

The square root of 172728991 is about 13142.6401837683. The cubic root of 172728991 is about 556.9143545385.

The spelling of 172728991 in words is "one hundred seventy-two million, seven hundred twenty-eight thousand, nine hundred ninety-one".