20500009 has 4 divisors (see below), whose sum is σ = 20510980. Its totient is φ = 20489040.

The previous prime is 20499971. The next prime is 20500019. The reversal of 20500009 is 90000502.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1315609 + 19184400 = 1147^2 + 4380^2 .

It is a cyclic number.

It is not a de Polignac number, because 20500009 - 2⁹ = 20499497 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20499965 and 20500001.

It is not an unprimeable number, because it can be changed into a prime (20500019) 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, 1902 + ... + 6679.

It is an arithmetic number, because the mean of its divisors is an integer number (5127745).

Almost surely, 2^20500009 is an apocalyptic number.

It is an amenable number.

20500009 is a deficient number, since it is larger than the sum of its proper divisors (10971).

20500009 is an equidigital number, since it uses as much as digits as its factorization.

20500009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10970.

The product of its (nonzero) digits is 90, while the sum is 16.

The square root of 20500009 is about 4527.6935629523. The cubic root of 20500009 is about 273.6852237914.

The spelling of 20500009 in words is "twenty million, five hundred thousand, nine".