20178121 has 4 divisors (see below), whose sum is σ = 20211652. Its totient is φ = 20144592.

The previous prime is 20178097. The next prime is 20178139. The reversal of 20178121 is 12187102.

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 3686400 + 16491721 = 1920^2 + 4061^2 .

It is a cyclic number.

It is not a de Polignac number, because 20178121 - 2⁵ = 20178089 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20178092 and 20178101.

It is not an unprimeable number, because it can be changed into a prime (20170121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15846 + ... + 17071.

It is an arithmetic number, because the mean of its divisors is an integer number (5052913).

Almost surely, 2^20178121 is an apocalyptic number.

It is an amenable number.

20178121 is a deficient number, since it is larger than the sum of its proper divisors (33531).

20178121 is an equidigital number, since it uses as much as digits as its factorization.

20178121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33530.

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 20178121 is about 4492.0063446082. The cubic root of 20178121 is about 272.2452058216.

The spelling of 20178121 in words is "twenty million, one hundred seventy-eight thousand, one hundred twenty-one".