209100816 has 120 divisors (see below), whose sum is σ = 623989080. Its totient is φ = 65138688.

The previous prime is 209100809. The next prime is 209100839. The reversal of 209100816 is 618001902.

It can be written as a sum of positive squares in 4 ways, for example, as 112275216 + 96825600 = 10596^2 + 9840^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 209100816.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 560406 + ... + 560778.

It is an arithmetic number, because the mean of its divisors is an integer number (5199909).

Almost surely, 2^209100816 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 209100816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (311994540).

209100816 is an abundant number, since it is smaller than the sum of its proper divisors (414888264).

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

209100816 is a wasteful number, since it uses less digits than its factorization.

209100816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 633 (or 624 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 209100816 is about 14460.3186686878. The cubic root of 209100816 is about 593.5426197129.

It can be divided in two parts, 209 and 100816, that added together give a triangular number (101025 = T₄₄₉).

The spelling of 209100816 in words is "two hundred nine million, one hundred thousand, eight hundred sixteen".