21086721216 has 168 divisors, whose sum is σ = 66063114000. Its totient is φ = 6377594880.

The previous prime is 21086721197. The next prime is 21086721217. The reversal of 21086721216 is 61212768012.

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 (21086721217) 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 23 ways as a sum of consecutive naturals, for example, 3602260 + ... + 3608108.

Almost surely, 2^21086721216 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 21086721216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33031557000).

21086721216 is an abundant number, since it is smaller than the sum of its proper divisors (44976392784).

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

21086721216 is a wasteful number, since it uses less digits than its factorization.

21086721216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6447 (or 6434 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The spelling of 21086721216 in words is "twenty-one billion, eighty-six million, seven hundred twenty-one thousand, two hundred sixteen".