209121220 has 144 divisors (see below), whose sum is σ = 587200320. Its totient is φ = 61689600.

The previous prime is 209121217. The next prime is 209121223. The reversal of 209121220 is 22121902.

It is an interprime number because it is at equal distance from previous prime (209121217) and next prime (209121223).

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209121223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 204310 + ... + 205330.

It is an arithmetic number, because the mean of its divisors is an integer number (4077780).

Almost surely, 2^209121220 is an apocalyptic number.

209121220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 209121220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (293600160).

209121220 is an abundant number, since it is smaller than the sum of its proper divisors (378079100).

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

209121220 is a wasteful number, since it uses less digits than its factorization.

209121220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1074 (or 1065 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 209121220 is about 14461.0241684329. The cubic root of 209121220 is about 593.5619249934.

The spelling of 209121220 in words is "two hundred nine million, one hundred twenty-one thousand, two hundred twenty".