21638402240 has 224 divisors, whose sum is σ = 63927435264. Its totient is φ = 6793113600.

The previous prime is 21638402183. The next prime is 21638402243. The reversal of 21638402240 is 4220483612.

It is a tau number, because it is divible by the number of its divisors (224).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 21638402197 and 21638402206.

It is not an unprimeable number, because it can be changed into a prime (21638402243) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3695315 + ... + 3701165.

It is an arithmetic number, because the mean of its divisors is an integer number (285390336).

Almost surely, 2^21638402240 is an apocalyptic number.

21638402240 is a gapful number since it is divisible by the number (20) 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 21638402240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31963717632).

21638402240 is an abundant number, since it is smaller than the sum of its proper divisors (42289033024).

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

21638402240 is a wasteful number, since it uses less digits than its factorization.

21638402240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6015 (or 6005 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 32.

Adding to 21638402240 its reverse (4220483612), we get a palindrome (25858885852).

The spelling of 21638402240 in words is "twenty-one billion, six hundred thirty-eight million, four hundred two thousand, two hundred forty".