21390003 has 6 divisors (see below), whose sum is σ = 30896684. Its totient is φ = 14259996.

The previous prime is 21389999. The next prime is 21390007. The reversal of 21390003 is 30009312.

It is an interprime number because it is at equal distance from previous prime (21389999) and next prime (21390007).

It is not a de Polignac number, because 21390003 - 2² = 21389999 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21390007) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1188325 + ... + 1188342.

Almost surely, 2^21390003 is an apocalyptic number.

21390003 is a deficient number, since it is larger than the sum of its proper divisors (9506681).

21390003 is a wasteful number, since it uses less digits than its factorization.

21390003 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2376673 (or 2376670 counting only the distinct ones).

The product of its (nonzero) digits is 162, while the sum is 18.

The square root of 21390003 is about 4624.9327562679. The cubic root of 21390003 is about 277.5898710617.

Adding to 21390003 its reverse (30009312), we get a palindrome (51399315).

The spelling of 21390003 in words is "twenty-one million, three hundred ninety thousand, three".