21558121200 has 720 divisors, whose sum is σ = 94497451776. Its totient is φ = 4420915200.

The previous prime is 21558121177. The next prime is 21558121279. The reversal of 21558121200 is 212185512.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (720).

It is a congruent number.

It is an unprimeable number.

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 143 ways as a sum of consecutive naturals, for example, 23007132 + ... + 23008068.

Almost surely, 2^21558121200 is an apocalyptic number.

21558121200 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 21558121200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47248725888).

21558121200 is an abundant number, since it is smaller than the sum of its proper divisors (72939330576).

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

21558121200 is a wasteful number, since it uses less digits than its factorization.

21558121200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1062 (or 1048 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 27.

The spelling of 21558121200 in words is "twenty-one billion, five hundred fifty-eight million, one hundred twenty-one thousand, two hundred".