21030523 has 4 divisors (see below), whose sum is σ = 21238848. Its totient is φ = 20822200.

The previous prime is 21030469. The next prime is 21030551. The reversal of 21030523 is 32503012.

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 21030523 - 2¹⁷ = 20899451 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21030497 and 21030506.

It is not an unprimeable number, because it can be changed into a prime (21030553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 104011 + ... + 104212.

It is an arithmetic number, because the mean of its divisors is an integer number (5309712).

Almost surely, 2^21030523 is an apocalyptic number.

21030523 is a deficient number, since it is larger than the sum of its proper divisors (208325).

21030523 is a wasteful number, since it uses less digits than its factorization.

21030523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208324.

The product of its (nonzero) digits is 180, while the sum is 16.

The square root of 21030523 is about 4585.9048180266. The cubic root of 21030523 is about 276.0260206161.

Adding to 21030523 its reverse (32503012), we get a palindrome (53533535).

The spelling of 21030523 in words is "twenty-one million, thirty thousand, five hundred twenty-three".