21312003 has 4 divisors (see below), whose sum is σ = 28416008. Its totient is φ = 14208000.

The previous prime is 21312001. The next prime is 21312017. The reversal of 21312003 is 30021312.

It is a happy number.

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

It is not a de Polignac number, because 21312003 - 2¹ = 21312001 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21312003.

It is not an unprimeable number, because it can be changed into a prime (21312001) 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, 3551998 + ... + 3552003.

It is an arithmetic number, because the mean of its divisors is an integer number (7104002).

Almost surely, 2^21312003 is an apocalyptic number.

21312003 is a deficient number, since it is larger than the sum of its proper divisors (7104005).

21312003 is an equidigital number, since it uses as much as digits as its factorization.

21312003 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7104004.

The product of its (nonzero) digits is 36, while the sum is 12.

The square root of 21312003 is about 4616.4924997231. The cubic root of 21312003 is about 277.2520437463.

Adding to 21312003 its reverse (30021312), we get a palindrome (51333315).

The spelling of 21312003 in words is "twenty-one million, three hundred twelve thousand, three".