21003828 has 12 divisors (see below), whose sum is σ = 49008960. Its totient is φ = 7001272.

The previous prime is 21003821. The next prime is 21003869. The reversal of 21003828 is 82830012.

It is a tau number, because it is divible by the number of its divisors (12).

It is a junction number, because it is equal to n+sod(n) for n = 21003798 and 21003807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003821) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 875148 + ... + 875171.

It is an arithmetic number, because the mean of its divisors is an integer number (4084080).

Almost surely, 2^21003828 is an apocalyptic number.

It is an amenable number.

21003828 is an abundant number, since it is smaller than the sum of its proper divisors (28005132).

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

21003828 is a wasteful number, since it uses less digits than its factorization.

21003828 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1750326 (or 1750324 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21003828 is about 4582.9933449657. The cubic root of 21003828 is about 275.9091803684.

The spelling of 21003828 in words is "twenty-one million, three thousand, eight hundred twenty-eight".