20172881 has 4 divisors (see below), whose sum is σ = 20718132. Its totient is φ = 19627632.

The previous prime is 20172877. The next prime is 20172941. The reversal of 20172881 is 18827102.

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

It can be written as a sum of positive squares in 2 ways, for example, as 14508481 + 5664400 = 3809^2 + 2380^2 .

It is a cyclic number.

It is not a de Polignac number, because 20172881 - 2² = 20172877 is a prime.

It is a super-2 number, since 2×20172881² = 813890255680322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20172781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 272570 + ... + 272643.

It is an arithmetic number, because the mean of its divisors is an integer number (5179533).

Almost surely, 2^20172881 is an apocalyptic number.

It is an amenable number.

20172881 is a deficient number, since it is larger than the sum of its proper divisors (545251).

20172881 is an equidigital number, since it uses as much as digits as its factorization.

20172881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 545250.

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 20172881 is about 4491.4230484335. The cubic root of 20172881 is about 272.2216375819.

Adding to 20172881 its reverse (18827102), we get a palindrome (38999983).

The spelling of 20172881 in words is "twenty million, one hundred seventy-two thousand, eight hundred eighty-one".