21321523 has 2 divisors, whose sum is σ = 21321524. Its totient is φ = 21321522.

The previous prime is 21321499. The next prime is 21321527. The reversal of 21321523 is 32512312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21321523 - 2¹⁷ = 21190451 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21321523.

It is not a weakly prime, because it can be changed into another prime (21321527) 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 as a sum of consecutive naturals, namely, 10660761 + 10660762.

It is an arithmetic number, because the mean of its divisors is an integer number (10660762).

It is a self-describing number.

Almost surely, 2^21321523 is an apocalyptic number.

21321523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21321523 is an equidigital number, since it uses as much as digits as its factorization.

21321523 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 360, while the sum is 19.

The square root of 21321523 is about 4617.5234704330. The cubic root of 21321523 is about 277.2933201192.

Adding to 21321523 its reverse (32512312), we get a palindrome (53833835).

It can be divided in two parts, 2132 and 1523, that added together give a triangular number (3655 = T₈₅).

The spelling of 21321523 in words is "twenty-one million, three hundred twenty-one thousand, five hundred twenty-three".