20936809 has 4 divisors (see below), whose sum is σ = 22168404. Its totient is φ = 19705216.

The previous prime is 20936807. The next prime is 20936819. The reversal of 20936809 is 90863902.

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 9734400 + 11202409 = 3120^2 + 3347^2 .

It is a cyclic number.

It is not a de Polignac number, because 20936809 - 2¹ = 20936807 is a prime.

It is a super-2 number, since 2×20936809² = 876699942204962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20936807) 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, 615772 + ... + 615805.

It is an arithmetic number, because the mean of its divisors is an integer number (5542101).

Almost surely, 2^20936809 is an apocalyptic number.

It is an amenable number.

20936809 is a deficient number, since it is larger than the sum of its proper divisors (1231595).

20936809 is a wasteful number, since it uses less digits than its factorization.

20936809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1231594.

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 20936809 is about 4575.6757970818. The cubic root of 20936809 is about 275.6154107520.

The spelling of 20936809 in words is "twenty million, nine hundred thirty-six thousand, eight hundred nine".