21003013 has 4 divisors (see below), whose sum is σ = 21570700. Its totient is φ = 20435328.

The previous prime is 21003011. The next prime is 21003053. The reversal of 21003013 is 31030012.

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

It can be written as a sum of positive squares in 2 ways, for example, as 8485569 + 12517444 = 2913^2 + 3538^2 .

It is a cyclic number.

It is not a de Polignac number, because 21003013 - 2¹ = 21003011 is a prime.

It is a super-2 number, since 2×21003013² = 882253110156338, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003011) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 283788 + ... + 283861.

It is an arithmetic number, because the mean of its divisors is an integer number (5392675).

Almost surely, 2^21003013 is an apocalyptic number.

It is an amenable number.

21003013 is a deficient number, since it is larger than the sum of its proper divisors (567687).

21003013 is an equidigital number, since it uses as much as digits as its factorization.

21003013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 567686.

The product of its (nonzero) digits is 18, while the sum is 10.

The square root of 21003013 is about 4582.9044284165. The cubic root of 21003013 is about 275.9056116715.

Adding to 21003013 its reverse (31030012), we get a palindrome (52033025).

The spelling of 21003013 in words is "twenty-one million, three thousand, thirteen".