21117205400 has 72 divisors (see below), whose sum is σ = 50271386220. Its totient is φ = 8245177920.

The previous prime is 21117205339. The next prime is 21117205433. The reversal of 21117205400 is 450271112.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 13475417 + ... + 13476983.

Almost surely, 2^21117205400 is an apocalyptic number.

21117205400 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 21117205400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25135693110).

21117205400 is an abundant number, since it is smaller than the sum of its proper divisors (29154180820).

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

21117205400 is an equidigital number, since it uses as much as digits as its factorization.

21117205400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3193 (or 1617 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 23.

Adding to 21117205400 its reverse (450271112), we get a palindrome (21567476512).

The spelling of 21117205400 in words is "twenty-one billion, one hundred seventeen million, two hundred five thousand, four hundred".