21644862640128 has 832 divisors, whose sum is σ = 81470280908800. Its totient is φ = 5524309278720.

The previous prime is 21644862640117. The next prime is 21644862640183. The reversal of 21644862640128 is 82104626844612.

21644862640128 is a `hidden beast` number, since 2 + 1 + 6 + 4 + 4 + 8 + 626 + 4 + 0 + 1 + 2 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (832).

It is a hoax number, since the sum of its digits (54) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 311945343 + ... + 312014721.

Almost surely, 2^{21644862640128} is an apocalyptic number.

21644862640128 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 21644862640128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40735140454400).

21644862640128 is an abundant number, since it is smaller than the sum of its proper divisors (59825418268672).

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

21644862640128 is a wasteful number, since it uses less digits than its factorization.

21644862640128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69463 (or 69435 counting only the distinct ones).

The product of its (nonzero) digits is 7077888, while the sum is 54.

The spelling of 21644862640128 in words is "twenty-one trillion, six hundred forty-four billion, eight hundred sixty-two million, six hundred forty thousand, one hundred twenty-eight".