21204423240 has 768 divisors, whose sum is σ = 88441528320. Its totient is φ = 3946475520.

The previous prime is 21204423217. The next prime is 21204423241. The reversal of 21204423240 is 4232440212.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21204423240.

It is not an unprimeable number, because it can be changed into a prime (21204423241) by changing a digit.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 57777537 + ... + 57777903.

It is an arithmetic number, because the mean of its divisors is an integer number (115158240).

Almost surely, 2^21204423240 is an apocalyptic number.

21204423240 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 21204423240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44220764160).

21204423240 is an abundant number, since it is smaller than the sum of its proper divisors (67237105080).

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

21204423240 is a wasteful number, since it uses less digits than its factorization.

21204423240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 462 (or 445 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 24.

Adding to 21204423240 its reverse (4232440212), we get a palindrome (25436863452).

It can be divided in two parts, 21204 and 423240, that added together give a palindrome (444444).

The spelling of 21204423240 in words is "twenty-one billion, two hundred four million, four hundred twenty-three thousand, two hundred forty".