21609215208 has 384 divisors, whose sum is σ = 75398688000. Its totient is φ = 5700119040.

The previous prime is 21609215207. The next prime is 21609215293. The reversal of 21609215208 is 80251290612.

21609215208 is a `hidden beast` number, since 2 + 1 + 609 + 21 + 5 + 20 + 8 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21609215207) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 7057998 + ... + 7061058.

It is an arithmetic number, because the mean of its divisors is an integer number (196350750).

Almost surely, 2^21609215208 is an apocalyptic number.

21609215208 is a gapful number since it is divisible by the number (28) 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 21609215208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37699344000).

21609215208 is an abundant number, since it is smaller than the sum of its proper divisors (53789472792).

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

21609215208 is a wasteful number, since it uses less digits than its factorization.

21609215208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3142 (or 3125 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The spelling of 21609215208 in words is "twenty-one billion, six hundred nine million, two hundred fifteen thousand, two hundred eight".