21504123240 has 256 divisors, whose sum is σ = 72781977600. Its totient is φ = 5055519744.

The previous prime is 21504123163. The next prime is 21504123253. The reversal of 21504123240 is 4232140512.

It is a super-2 number, since 2×21504123240² (a number of 21 digits) contains 22 as substring.

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 21504123240.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1934739 + ... + 1945821.

It is an arithmetic number, because the mean of its divisors is an integer number (284304600).

Almost surely, 2^21504123240 is an apocalyptic number.

21504123240 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 21504123240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36390988800).

21504123240 is an abundant number, since it is smaller than the sum of its proper divisors (51277854360).

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

21504123240 is a wasteful number, since it uses less digits than its factorization.

21504123240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11176 (or 11172 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 24.

Adding to 21504123240 its reverse (4232140512), we get a palindrome (25736263752).

The spelling of 21504123240 in words is "twenty-one billion, five hundred four million, one hundred twenty-three thousand, two hundred forty".