21000320 has 128 divisors (see below), whose sum is σ = 58017600. Its totient is φ = 7188480.

The previous prime is 21000313. The next prime is 21000337. The reversal of 21000320 is 2300012.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (8).

It is a junction number, because it is equal to n+sod(n) for n = 21000298 and 21000307.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 133682 + ... + 133838.

Almost surely, 2^21000320 is an apocalyptic number.

21000320 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 21000320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29008800).

21000320 is an abundant number, since it is smaller than the sum of its proper divisors (37017280).

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

21000320 is a wasteful number, since it uses less digits than its factorization.

21000320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206 (or 194 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 8.

The square root of 21000320 is about 4582.6106096853. The cubic root of 21000320 is about 275.8938189893.

Adding to 21000320 its reverse (2300012), we get a palindrome (23300332).

The spelling of 21000320 in words is "twenty-one million, three hundred twenty", and thus it is an aban number.