21213765216 has 480 divisors, whose sum is σ = 73766246400. Its totient is φ = 5977504512.

The previous prime is 21213765173. The next prime is 21213765233. The reversal of 21213765216 is 61256731212.

21213765216 is a `hidden beast` number, since 2 + 121 + 3 + 7 + 6 + 521 + 6 = 666.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 95128881 + ... + 95129103.

It is an arithmetic number, because the mean of its divisors is an integer number (153679680).

Almost surely, 2^21213765216 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 21213765216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36883123200).

21213765216 is an abundant number, since it is smaller than the sum of its proper divisors (52552481184).

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

21213765216 is a wasteful number, since it uses less digits than its factorization.

21213765216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 373 (or 342 counting only the distinct ones).

The product of its digits is 30240, while the sum is 36.

The spelling of 21213765216 in words is "twenty-one billion, two hundred thirteen million, seven hundred sixty-five thousand, two hundred sixteen".