21003023 has 4 divisors (see below), whose sum is σ = 21021240. Its totient is φ = 20984808.

The previous prime is 21003011. The next prime is 21003053. The reversal of 21003023 is 32030012.

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 21003023 - 2⁸ = 21002767 is a prime.

It is a super-2 number, since 2×21003023² = 882253950277058, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21002995 and 21003013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003053) 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, 7253 + ... + 9726.

It is an arithmetic number, because the mean of its divisors is an integer number (5255310).

Almost surely, 2^21003023 is an apocalyptic number.

21003023 is a deficient number, since it is larger than the sum of its proper divisors (18217).

21003023 is a wasteful number, since it uses less digits than its factorization.

21003023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18216.

The product of its (nonzero) digits is 36, while the sum is 11.

The square root of 21003023 is about 4582.9055194276. The cubic root of 21003023 is about 275.9056554597.

Adding to 21003023 its reverse (32030012), we get a palindrome (53033035).

The spelling of 21003023 in words is "twenty-one million, three thousand, twenty-three".