209121020 has 12 divisors (see below), whose sum is σ = 439154184. Its totient is φ = 83648400.

The previous prime is 209121007. The next prime is 209121023. The reversal of 209121020 is 20121902.

It is a self number, because there is not a number n which added to its sum of digits gives 209121020.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209121023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5228006 + ... + 5228045.

It is an arithmetic number, because the mean of its divisors is an integer number (36596182).

Almost surely, 2^209121020 is an apocalyptic number.

209121020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

209121020 is an abundant number, since it is smaller than the sum of its proper divisors (230033164).

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

209121020 is a wasteful number, since it uses less digits than its factorization.

209121020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10456060 (or 10456058 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 209121020 is about 14461.0172532917. The cubic root of 209121020 is about 593.5617357692.

Adding to 209121020 its reverse (20121902), we get a palindrome (229242922).

The spelling of 209121020 in words is "two hundred nine million, one hundred twenty-one thousand, twenty".