20009509 has 4 divisors (see below), whose sum is σ = 21548716. Its totient is φ = 18470304.

The previous prime is 20009497. The next prime is 20009513. The reversal of 20009509 is 90590002.

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 6890625 + 13118884 = 2625^2 + 3622^2 .

It is a cyclic number.

It is not a de Polignac number, because 20009509 - 2¹⁷ = 19878437 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 (20009569) 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, 769584 + ... + 769609.

It is an arithmetic number, because the mean of its divisors is an integer number (5387179).

Almost surely, 2^20009509 is an apocalyptic number.

It is an amenable number.

20009509 is a deficient number, since it is larger than the sum of its proper divisors (1539207).

20009509 is a wasteful number, since it uses less digits than its factorization.

20009509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1539206.

The product of its (nonzero) digits is 810, while the sum is 25.

The square root of 20009509 is about 4473.1989671822. The cubic root of 20009509 is about 271.4847738387.

The spelling of 20009509 in words is "twenty million, nine thousand, five hundred nine".