21121171200 has 486 divisors, whose sum is σ = 78569205624. Its totient is φ = 5621114880.

The previous prime is 21121171151. The next prime is 21121171237. The reversal of 21121171200 is 217112112.

It is a tau number, because it is divible by the number of its divisors (486).

It is a super-2 number, since 2×21121171200² (a number of 21 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (18) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (18).

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 53 ways as a sum of consecutive naturals, for example, 41990149 + ... + 41990651.

Almost surely, 2^21121171200 is an apocalyptic number.

21121171200 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 21121171200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39284602812).

21121171200 is an abundant number, since it is smaller than the sum of its proper divisors (57448034424).

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

21121171200 is an frugal number, since it uses more digits than its factorization.

21121171200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553 (or 513 counting only the distinct ones).

The product of its (nonzero) digits is 56, while the sum is 18.

Adding to 21121171200 its reverse (217112112), we get a palindrome (21338283312).

The spelling of 21121171200 in words is "twenty-one billion, one hundred twenty-one million, one hundred seventy-one thousand, two hundred".