20809216 has 40 divisors (see below), whose sum is σ = 42106680. Its totient is φ = 10272768.

The previous prime is 20809213. The next prime is 20809223. The reversal of 20809216 is 61290802.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20809213) 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, 49455 + ... + 49873.

It is an arithmetic number, because the mean of its divisors is an integer number (1052667).

Almost surely, 2^20809216 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20809216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21053340).

20809216 is an abundant number, since it is smaller than the sum of its proper divisors (21297464).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20809216 is an frugal number, since it uses more digits than its factorization.

20809216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534 (or 518 counting only the distinct ones).

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

The square root of 20809216 is about 4561.7119593416. The cubic root of 20809216 is about 275.0543848363.

It can be divided in two parts, 20809 and 216, that added together give a square (21025 = 145²).

The spelling of 20809216 in words is "twenty million, eight hundred nine thousand, two hundred sixteen".