21009443840 has 528 divisors, whose sum is σ = 66938275584. Its totient is φ = 6244761600.

The previous prime is 21009443839. The next prime is 21009443867. The reversal of 21009443840 is 4834490012.

It is a super-2 number, since 2×21009443840² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 21009443840.

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, 63472475 + ... + 63472805.

Almost surely, 2^21009443840 is an apocalyptic number.

21009443840 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 21009443840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33469137792).

21009443840 is an abundant number, since it is smaller than the sum of its proper divisors (45928831744).

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

21009443840 is a wasteful number, since it uses less digits than its factorization.

21009443840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404 (or 379 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 35.

The spelling of 21009443840 in words is "twenty-one billion, nine million, four hundred forty-three thousand, eight hundred forty".