21209886720 has 624 divisors, whose sum is σ = 83143236960. Its totient is φ = 5125570560.

The previous prime is 21209886703. The next prime is 21209886739. The reversal of 21209886720 is 2768890212.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 66908002 + ... + 66908318.

Almost surely, 2^21209886720 is an apocalyptic number.

21209886720 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 21209886720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41571618480).

21209886720 is an abundant number, since it is smaller than the sum of its proper divisors (61933350240).

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

21209886720 is a wasteful number, since it uses less digits than its factorization.

21209886720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 377 (or 338 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 45.

The spelling of 21209886720 in words is "twenty-one billion, two hundred nine million, eight hundred eighty-six thousand, seven hundred twenty".