21215827800 has 240 divisors, whose sum is σ = 74067246000. Its totient is φ = 5628268800.

The previous prime is 21215827799. The next prime is 21215827813. The reversal of 21215827800 is 872851212.

21215827800 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 582 + 78 + 0 + 0 = 666.

It is a super-2 number, since 2×21215827800² (a number of 21 digits) contains 22 as substring.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 3220510 + ... + 3227090.

It is an arithmetic number, because the mean of its divisors is an integer number (308613525).

Almost surely, 2^21215827800 is an apocalyptic number.

21215827800 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 21215827800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37033623000).

21215827800 is an abundant number, since it is smaller than the sum of its proper divisors (52851418200).

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

21215827800 is a wasteful number, since it uses less digits than its factorization.

21215827800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6808 (or 6790 counting only the distinct ones).

The product of its (nonzero) digits is 17920, while the sum is 36.

The spelling of 21215827800 in words is "twenty-one billion, two hundred fifteen million, eight hundred twenty-seven thousand, eight hundred".