20216809 has 4 divisors (see below), whose sum is σ = 20248704. Its totient is φ = 20184916.

The previous prime is 20216761. The next prime is 20216827. The reversal of 20216809 is 90861202.

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 20216809 - 2⁹ = 20216297 is a prime.

It is a super-2 number, since 2×20216809² = 817438732284962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20216869) 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, 14977 + ... + 16270.

It is an arithmetic number, because the mean of its divisors is an integer number (5062176).

Almost surely, 2^20216809 is an apocalyptic number.

It is an amenable number.

20216809 is a deficient number, since it is larger than the sum of its proper divisors (31895).

20216809 is an equidigital number, since it uses as much as digits as its factorization.

20216809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31894.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 20216809 is about 4496.3105987020. The cubic root of 20216809 is about 272.4190888474.

It can be divided in two parts, 20216 and 809, that added together give a square (21025 = 145²).

The spelling of 20216809 in words is "twenty million, two hundred sixteen thousand, eight hundred nine".