21251024520 has 256 divisors, whose sum is σ = 72668897280. Its totient is φ = 4924723200.

The previous prime is 21251024507. The next prime is 21251024549. The reversal of 21251024520 is 2542015212.

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

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, 3393232 + ... + 3399488.

It is an arithmetic number, because the mean of its divisors is an integer number (283862880).

Almost surely, 2^21251024520 is an apocalyptic number.

21251024520 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 21251024520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36334448640).

21251024520 is an abundant number, since it is smaller than the sum of its proper divisors (51417872760).

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

21251024520 is a wasteful number, since it uses less digits than its factorization.

21251024520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6396 (or 6392 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 24.

Adding to 21251024520 its reverse (2542015212), we get a palindrome (23793039732).

The spelling of 21251024520 in words is "twenty-one billion, two hundred fifty-one million, twenty-four thousand, five hundred twenty".