21221523 has 12 divisors (see below), whose sum is σ = 31023720. Its totient is φ = 13976736.

The previous prime is 21221521. The next prime is 21221531. The reversal of 21221523 is 32512212.

It is not a de Polignac number, because 21221523 - 2¹ = 21221521 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21221496 and 21221505.

It is not an unprimeable number, because it can be changed into a prime (21221521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13458 + ... + 14951.

It is an arithmetic number, because the mean of its divisors is an integer number (2585310).

Almost surely, 2^21221523 is an apocalyptic number.

21221523 is a deficient number, since it is larger than the sum of its proper divisors (9802197).

21221523 is a wasteful number, since it uses less digits than its factorization.

21221523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28498 (or 28495 counting only the distinct ones).

The product of its digits is 240, while the sum is 18.

The square root of 21221523 is about 4606.6824288201. The cubic root of 21221523 is about 276.8591298035.

Adding to 21221523 its reverse (32512212), we get a palindrome (53733735).

The spelling of 21221523 in words is "twenty-one million, two hundred twenty-one thousand, five hundred twenty-three".