21638388669984 has 240 divisors, whose sum is σ = 67437021777048. Its totient is φ = 6782900871168.

The previous prime is 21638388669983. The next prime is 21638388669991. The reversal of 21638388669984 is 48996688383612.

It is a happy number.

21638388669984 is a `hidden beast` number, since 2 + 16 + 3 + 8 + 388 + 66 + 99 + 84 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 9959957283600 + 11678431386384 = 3155940^2 + 3417372^2 .

It is a super-3 number, since 3×21638388669984³ (a number of 41 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (81).

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

It is not an unprimeable number, because it can be changed into a prime (21638388669983) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 53247214 + ... + 53652050.

Almost surely, 2^{21638388669984} is an apocalyptic number.

21638388669984 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 21638388669984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33718510888524).

21638388669984 is an abundant number, since it is smaller than the sum of its proper divisors (45798633107064).

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

21638388669984 is a wasteful number, since it uses less digits than its factorization.

21638388669984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406089 (or 406072 counting only the distinct ones).

The product of its digits is 5159780352, while the sum is 81.

The spelling of 21638388669984 in words is "twenty-one trillion, six hundred thirty-eight billion, three hundred eighty-eight million, six hundred sixty-nine thousand, nine hundred eighty-four".