21003680 has 48 divisors (see below), whose sum is σ = 49914144. Its totient is φ = 8352000.

The previous prime is 21003677. The next prime is 21003707. The reversal of 21003680 is 8630012.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39899 + ... + 40421.

It is an arithmetic number, because the mean of its divisors is an integer number (1039878).

Almost surely, 2^21003680 is an apocalyptic number.

21003680 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 21003680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24957072).

21003680 is an abundant number, since it is smaller than the sum of its proper divisors (28910464).

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

21003680 is a wasteful number, since it uses less digits than its factorization.

21003680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 789 (or 781 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21003680 is about 4582.9771982850. The cubic root of 21003680 is about 275.9085323174.

Adding to 21003680 its reverse (8630012), we get a palindrome (29633692).

The spelling of 21003680 in words is "twenty-one million, three thousand, six hundred eighty".