21210523 has 4 divisors (see below), whose sum is σ = 21230440. Its totient is φ = 21190608.

The previous prime is 21210521. The next prime is 21210529. The reversal of 21210523 is 32501212.

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 21210523 - 2¹ = 21210521 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 = 21210497 and 21210506.

It is not an unprimeable number, because it can be changed into a prime (21210521) 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, 8265 + ... + 10522.

It is an arithmetic number, because the mean of its divisors is an integer number (5307610).

Almost surely, 2^21210523 is an apocalyptic number.

21210523 is a deficient number, since it is larger than the sum of its proper divisors (19917).

21210523 is a wasteful number, since it uses less digits than its factorization.

21210523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19916.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21210523 is about 4605.4883562984. The cubic root of 21210523 is about 276.8112856601.

Adding to 21210523 its reverse (32501212), we get a palindrome (53711735).

The spelling of 21210523 in words is "twenty-one million, two hundred ten thousand, five hundred twenty-three".