21115987200 has 1620 divisors, whose sum is σ = 101757007968. Its totient is φ = 4196966400.

The previous prime is 21115987171. The next prime is 21115987201. The reversal of 21115987200 is 278951112.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (1620).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21115987201) by changing a digit.

It is a polite number, since it can be written in 179 ways as a sum of consecutive naturals, for example, 918086389 + ... + 918086411.

Almost surely, 2^21115987200 is an apocalyptic number.

21115987200 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 21115987200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (50878503984).

21115987200 is an abundant number, since it is smaller than the sum of its proper divisors (80641020768).

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

21115987200 is a wasteful number, since it uses less digits than its factorization.

21115987200 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102 (or 51 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 36.

The spelling of 21115987200 in words is "twenty-one billion, one hundred fifteen million, nine hundred eighty-seven thousand, two hundred".