21000003 has 8 divisors (see below), whose sum is σ = 28142928. Its totient is φ = 13928544.

The previous prime is 20999999. The next prime is 21000037. The reversal of 21000003 is 30000012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21000003 - 2² = 20999999 is a prime.

It is a super-4 number, since 4×21000003⁴ (a number of 30 digits) contains 4444 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20999955 and 21000000.

It is not an unprimeable number, because it can be changed into a prime (21000103) 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 7 ways as a sum of consecutive naturals, for example, 17176 + ... + 18357.

It is an arithmetic number, because the mean of its divisors is an integer number (3517866).

Almost surely, 2^21000003 is an apocalyptic number.

21000003 is a deficient number, since it is larger than the sum of its proper divisors (7142925).

21000003 is a wasteful number, since it uses less digits than its factorization.

21000003 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35733.

The product of its (nonzero) digits is 6, while the sum is 6.

The square root of 21000003 is about 4582.5760222827. The cubic root of 21000003 is about 275.8924307758.

Adding to 21000003 its reverse (30000012), we get a palindrome (51000015).

Subtracting 21000003 from its reverse (30000012), we obtain a palindrome (9000009).

The spelling of 21000003 in words is "twenty-one million, three", and thus it is an aban number and an uban number.