21010003 has 4 divisors (see below), whose sum is σ = 24011440. Its totient is φ = 18008568.

The previous prime is 21009997. The next prime is 21010013. The reversal of 21010003 is 30001012.

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 21010003 - 2⁹ = 21009491 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (7), and also a Moran number because the ratio is a prime number: 3001429 = 21010003 / (2 + 1 + 0 + 1 + 0 + 0 + 0 + 3).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21010013) 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, 1500708 + ... + 1500721.

It is an arithmetic number, because the mean of its divisors is an integer number (6002860).

Almost surely, 2^21010003 is an apocalyptic number.

21010003 is a deficient number, since it is larger than the sum of its proper divisors (3001437).

21010003 is an equidigital number, since it uses as much as digits as its factorization.

21010003 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3001436.

The product of its (nonzero) digits is 6, while the sum is 7.

The square root of 21010003 is about 4583.6669817953. Note that the first 3 decimals coincide. The cubic root of 21010003 is about 275.9362162696.

Adding to 21010003 its reverse (30001012), we get a palindrome (51011015).

The spelling of 21010003 in words is "twenty-one million, ten thousand, three".