21209844496 has 45 divisors (see below), whose sum is σ = 42985609639. Its totient is φ = 10137430688.

The previous prime is 21209844493. The next prime is 21209844577. The reversal of 21209844496 is 69444890212.

It is a happy number.

The square root of 21209844496 is 145636.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21209844493) 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 8 ways as a sum of consecutive naturals, for example, 13397721 + ... + 13399303.

Almost surely, 2^21209844496 is an apocalyptic number.

21209844496 is the 145636-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21209844496

21209844496 is an abundant number, since it is smaller than the sum of its proper divisors (21775765143).

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

21209844496 is an frugal number, since it uses more digits than its factorization.

21209844496 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3220 (or 1608 counting only the distinct ones).

The product of its (nonzero) digits is 995328, while the sum is 49.

Multiplying 21209844496 by its sum of digits (49), we get a square (1039282380304 = 1019452²).

The spelling of 21209844496 in words is "twenty-one billion, two hundred nine million, eight hundred forty-four thousand, four hundred ninety-six".