21851641728 has 192 divisors, whose sum is σ = 75022693200. Its totient is φ = 6243277824.

The previous prime is 21851641703. The next prime is 21851641741. The reversal of 21851641728 is 82714615812.

21851641728 is a `hidden beast` number, since 21 + 8 + 516 + 41 + 72 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (192).

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, 104826 + ... + 233862.

Almost surely, 2^21851641728 is an apocalyptic number.

21851641728 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 21851641728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37511346600).

21851641728 is an abundant number, since it is smaller than the sum of its proper divisors (53171051472).

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

21851641728 is a wasteful number, since it uses less digits than its factorization.

21851641728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129074 (or 129049 counting only the distinct ones).

The product of its digits is 215040, while the sum is 45.

The spelling of 21851641728 in words is "twenty-one billion, eight hundred fifty-one million, six hundred forty-one thousand, seven hundred twenty-eight".