20509121 has 4 divisors (see below), whose sum is σ = 20579412. Its totient is φ = 20438832.

The previous prime is 20509117. The next prime is 20509127. The reversal of 20509121 is 12190502.

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 18447025 + 2062096 = 4295^2 + 1436^2 .

It is a cyclic number.

It is not a de Polignac number, because 20509121 - 2² = 20509117 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20509093 and 20509102.

It is not an unprimeable number, because it can be changed into a prime (20509127) 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, 34706 + ... + 35291.

It is an arithmetic number, because the mean of its divisors is an integer number (5144853).

Almost surely, 2^20509121 is an apocalyptic number.

It is an amenable number.

20509121 is a deficient number, since it is larger than the sum of its proper divisors (70291).

20509121 is an equidigital number, since it uses as much as digits as its factorization.

20509121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70290.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 20509121 is about 4528.6997030053. The cubic root of 20509121 is about 273.7257676819.

Adding to 20509121 its reverse (12190502), we get a palindrome (32699623).

The spelling of 20509121 in words is "twenty million, five hundred nine thousand, one hundred twenty-one".