21306564216 has 128 divisors (see below), whose sum is σ = 67701312000. Its totient is φ = 6082062336.

The previous prime is 21306564179. The next prime is 21306564221. The reversal of 21306564216 is 61246560312.

21306564216 is a `hidden beast` number, since 2 + 1 + 3 + 0 + 6 + 5 + 642 + 1 + 6 = 666.

It is a super-3 number, since 3×21306564216³ (a number of 32 digits) contains 333 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 31 ways as a sum of consecutive naturals, for example, 1834315 + ... + 1845893.

It is an arithmetic number, because the mean of its divisors is an integer number (528916500).

Almost surely, 2^21306564216 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 21306564216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33850656000).

21306564216 is an abundant number, since it is smaller than the sum of its proper divisors (46394747784).

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

21306564216 is a wasteful number, since it uses less digits than its factorization.

21306564216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12818 (or 12808 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The spelling of 21306564216 in words is "twenty-one billion, three hundred six million, five hundred sixty-four thousand, two hundred sixteen".