21011003 has 4 divisors (see below), whose sum is σ = 22627248. Its totient is φ = 19394760.

The previous prime is 21010987. The next prime is 21011009. The reversal of 21011003 is 30011012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21011003 - 2⁴ = 21010987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21011009) 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, 808103 + ... + 808128.

It is an arithmetic number, because the mean of its divisors is an integer number (5656812).

Almost surely, 2^21011003 is an apocalyptic number.

21011003 is a deficient number, since it is larger than the sum of its proper divisors (1616245).

21011003 is a wasteful number, since it uses less digits than its factorization.

21011003 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1616244.

The product of its (nonzero) digits is 6, while the sum is 8.

The square root of 21011003 is about 4583.7760634656. The cubic root of 21011003 is about 275.9405940547.

Adding to 21011003 its reverse (30011012), we get a palindrome (51022015).

Subtracting 21011003 from its reverse (30011012), we obtain a palindrome (9000009).

The spelling of 21011003 in words is "twenty-one million, eleven thousand, three".