21115243500 has 192 divisors, whose sum is σ = 67629219840. Its totient is φ = 5086790400.

The previous prime is 21115243493. The next prime is 21115243507. The reversal of 21115243500 is 534251112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21115243493) and next prime (21115243507).

It is not an unprimeable number, because it can be changed into a prime (21115243507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 904981 + ... + 928019.

It is an arithmetic number, because the mean of its divisors is an integer number (352235520).

Almost surely, 2^21115243500 is an apocalyptic number.

21115243500 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 21115243500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33814609920).

21115243500 is an abundant number, since it is smaller than the sum of its proper divisors (46513976340).

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

21115243500 is a wasteful number, since it uses less digits than its factorization.

21115243500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23121 (or 23109 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 24.

Adding to 21115243500 its reverse (534251112), we get a palindrome (21649494612).

The spelling of 21115243500 in words is "twenty-one billion, one hundred fifteen million, two hundred forty-three thousand, five hundred".