21115500000 has 336 divisors, whose sum is σ = 79221485952. Its totient is φ = 4824000000.

The previous prime is 21115499989. The next prime is 21115500019. The reversal of 21115500000 is 551112.

It is a tau number, because it is divible by the number of its divisors (336).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 10498995 + ... + 10501005.

It is an arithmetic number, because the mean of its divisors is an integer number (235778232).

Almost surely, 2^21115500000 is an apocalyptic number.

21115500000 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 21115500000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39610742976).

21115500000 is an abundant number, since it is smaller than the sum of its proper divisors (58105985952).

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

21115500000 is an frugal number, since it uses more digits than its factorization.

21115500000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2061 (or 2028 counting only the distinct ones).

The product of its (nonzero) digits is 50, while the sum is 15.

The spelling of 21115500000 in words is "twenty-one billion, one hundred fifteen million, five hundred thousand".