21085944100 has 81 divisors (see below), whose sum is σ = 49591374777. Its totient is φ = 7778609280.

The previous prime is 21085944049. The next prime is 21085944119. The reversal of 21085944100 is 144958012.

It is a happy number.

The square root of 21085944100 is 145210.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 13 ways, for example, as 18992698596 + 2093245504 = 137814^2 + 45752^2 .

It is a Duffinian 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 26 ways as a sum of consecutive naturals, for example, 18876742 + ... + 18877858.

Almost surely, 2^21085944100 is an apocalyptic number.

21085944100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21085944100 is the 145210-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21085944100

21085944100 is an abundant number, since it is smaller than the sum of its proper divisors (28505430677).

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

21085944100 is a wasteful number, since it uses less digits than its factorization.

21085944100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2274 (or 1137 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 34.

The spelling of 21085944100 in words is "twenty-one billion, eighty-five million, nine hundred forty-four thousand, one hundred".