21616651728 has 240 divisors, whose sum is σ = 74555644800. Its totient is φ = 5708206080.

The previous prime is 21616651697. The next prime is 21616651753. The reversal of 21616651728 is 82715661612.

21616651728 is a `hidden beast` number, since 2 + 1 + 616 + 6 + 5 + 1 + 7 + 28 = 666.

It is a congruent number.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 771468 + ... + 798996.

It is an arithmetic number, because the mean of its divisors is an integer number (310648520).

Almost surely, 2^21616651728 is an apocalyptic number.

21616651728 is a gapful number since it is divisible by the number (28) 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 21616651728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37277822400).

21616651728 is an abundant number, since it is smaller than the sum of its proper divisors (52938993072).

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

21616651728 is a wasteful number, since it uses less digits than its factorization.

21616651728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27610 (or 27601 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The spelling of 21616651728 in words is "twenty-one billion, six hundred sixteen million, six hundred fifty-one thousand, seven hundred twenty-eight".