21001000320 has 384 divisors, whose sum is σ = 78672746880. Its totient is φ = 5141299200.

The previous prime is 21001000309. The next prime is 21001000343. The reversal of 21001000320 is 2300010012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (384).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4012105 + ... + 4017335.

It is an arithmetic number, because the mean of its divisors is an integer number (204876945).

Almost surely, 2^21001000320 is an apocalyptic number.

21001000320 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 21001000320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39336373440).

21001000320 is an abundant number, since it is smaller than the sum of its proper divisors (57671746560).

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

21001000320 is a wasteful number, since it uses less digits than its factorization.

21001000320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5314 (or 5299 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

Adding to 21001000320 its reverse (2300010012), we get a palindrome (23301010332).

The spelling of 21001000320 in words is "twenty-one billion, one million, three hundred twenty", and thus it is an aban number.