20807809 has 4 divisors (see below), whose sum is σ = 22699440. Its totient is φ = 18916180.

The previous prime is 20807803. The next prime is 20807833. The reversal of 20807809 is 90870802.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20807809 - 2¹⁹ = 20283521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20807803) 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, 945799 + ... + 945820.

It is an arithmetic number, because the mean of its divisors is an integer number (5674860).

Almost surely, 2^20807809 is an apocalyptic number.

It is an amenable number.

20807809 is a deficient number, since it is larger than the sum of its proper divisors (1891631).

20807809 is a wasteful number, since it uses less digits than its factorization.

20807809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1891630.

The product of its (nonzero) digits is 8064, while the sum is 34.

The square root of 20807809 is about 4561.5577383170. The cubic root of 20807809 is about 275.0481854958.

It can be divided in two parts, 2080 and 7809, that added together give a palindrome (9889).

The spelling of 20807809 in words is "twenty million, eight hundred seven thousand, eight hundred nine".