21099905600 has 252 divisors, whose sum is σ = 55047338724. Its totient is φ = 7958691840.

The previous prime is 21099905591. The next prime is 21099905609. The reversal of 21099905600 is 650999012.

It is an interprime number because it is at equal distance from previous prime (21099905591) and next prime (21099905609).

It can be written as a sum of positive squares in 6 ways, for example, as 554696704 + 20545208896 = 23552^2 + 143336^2 .

It is a super-2 number, since 2×21099905600² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21099905609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 82100672 + ... + 82100928.

Almost surely, 2^21099905600 is an apocalyptic number.

21099905600 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 21099905600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27523669362).

21099905600 is an abundant number, since it is smaller than the sum of its proper divisors (33947433124).

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

21099905600 is a wasteful number, since it uses less digits than its factorization.

21099905600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 422 (or 384 counting only the distinct ones).

The product of its (nonzero) digits is 43740, while the sum is 41.

The spelling of 21099905600 in words is "twenty-one billion, ninety-nine million, nine hundred five thousand, six hundred".