21636513216 has 168 divisors, whose sum is σ = 63159071040. Its totient is φ = 7080321024.

The previous prime is 21636513191. The next prime is 21636513221. The reversal of 21636513216 is 61231563612.

21636513216 is a `hidden beast` number, since 2 + 1 + 636 + 5 + 1 + 3 + 2 + 16 = 666.

It is a super-2 number, since 2×21636513216² (a number of 21 digits) contains 22 as substring.

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 23 ways as a sum of consecutive naturals, for example, 10048396 + ... + 10050548.

Almost surely, 2^21636513216 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 21636513216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31579535520).

21636513216 is an abundant number, since it is smaller than the sum of its proper divisors (41522557824).

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

21636513216 is a wasteful number, since it uses less digits than its factorization.

21636513216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2483 (or 2470 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The spelling of 21636513216 in words is "twenty-one billion, six hundred thirty-six million, five hundred thirteen thousand, two hundred sixteen".