21636066816 has 840 divisors, whose sum is σ = 81847774800. Its totient is φ = 5706215424.

The previous prime is 21636066797. The next prime is 21636066817. The reversal of 21636066816 is 61866063612.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

21636066816 is a `hidden beast` number, since 2 + 1 + 636 + 0 + 6 + 6 + 8 + 1 + 6 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21636066817) by changing a digit.

It is a polite number, since it can be written in 83 ways as a sum of consecutive naturals, for example, 1664312826 + ... + 1664312838.

Almost surely, 2^21636066816 is an apocalyptic number.

21636066816 is a gapful number since it is divisible by the number (26) 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 21636066816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40923887400).

21636066816 is an abundant number, since it is smaller than the sum of its proper divisors (60211707984).

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

21636066816 is an frugal number, since it uses more digits than its factorization.

21636066816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83 (or 25 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The spelling of 21636066816 in words is "twenty-one billion, six hundred thirty-six million, sixty-six thousand, eight hundred sixteen".