21701665649664 has 2112 divisors, whose sum is σ = 87981208154112. Its totient is φ = 5159780352000.

The previous prime is 21701665649639. The next prime is 21701665649687. The reversal of 21701665649664 is 46694656610712.

21701665649664 is a `hidden beast` number, since 2 + 1 + 7 + 0 + 1 + 6 + 6 + 564 + 9 + 6 + 64 = 666.

It is a tau number, because it is divible by the number of its divisors (2112).

It is a Harshad number since it is a multiple of its sum of digits (63).

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 191 ways as a sum of consecutive naturals, for example, 37611205344 + ... + 37611205920.

Almost surely, 2^{21701665649664} is an apocalyptic number.

21701665649664 is a gapful number since it is divisible by the number (24) 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 21701665649664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43990604077056).

21701665649664 is an abundant number, since it is smaller than the sum of its proper divisors (66279542504448).

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

21701665649664 is a wasteful number, since it uses less digits than its factorization.

21701665649664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 794 (or 764 counting only the distinct ones).

The product of its (nonzero) digits is 78382080, while the sum is 63.

The spelling of 21701665649664 in words is "twenty-one trillion, seven hundred one billion, six hundred sixty-five million, six hundred forty-nine thousand, six hundred sixty-four".