21109745664 has 600 divisors, whose sum is σ = 74945600730. Its totient is φ = 5917556736.

The previous prime is 21109745663. The next prime is 21109745689. The reversal of 21109745664 is 46654790112.

21109745664 is a `hidden beast` number, since 2 + 1 + 10 + 9 + 74 + 566 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 16131032064 + 4978713600 = 127008^2 + 70560^2 .

It is not an unprimeable number, because it can be changed into a prime (21109745663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 49 ways as a sum of consecutive naturals, for example, 398297062 + ... + 398297114.

Almost surely, 2^21109745664 is an apocalyptic number.

21109745664 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 21109745664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37472800365).

21109745664 is an abundant number, since it is smaller than the sum of its proper divisors (53835855066).

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

21109745664 is an frugal number, since it uses more digits than its factorization.

21109745664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115 (or 65 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 45.

The spelling of 21109745664 in words is "twenty-one billion, one hundred nine million, seven hundred forty-five thousand, six hundred sixty-four".