21291941664 has 192 divisors, whose sum is σ = 72137882880. Its totient is φ = 5983580160.

The previous prime is 21291941659. The next prime is 21291941677. The reversal of 21291941664 is 46614919212.

21291941664 is a `hidden beast` number, since 212 + 9 + 19 + 416 + 6 + 4 = 666.

It is a nude number because it is divisible by every one of its digits.

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 31 ways as a sum of consecutive naturals, for example, 340072 + ... + 397784.

It is an arithmetic number, because the mean of its divisors is an integer number (375718140).

Almost surely, 2^21291941664 is an apocalyptic number.

21291941664 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 21291941664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36068941440).

21291941664 is an abundant number, since it is smaller than the sum of its proper divisors (50845941216).

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

21291941664 is a wasteful number, since it uses less digits than its factorization.

21291941664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57800 (or 57786 counting only the distinct ones).

The product of its digits is 186624, while the sum is 45.

The spelling of 21291941664 in words is "twenty-one billion, two hundred ninety-one million, nine hundred forty-one thousand, six hundred sixty-four".