21331523 has 2 divisors, whose sum is σ = 21331524. Its totient is φ = 21331522.

The previous prime is 21331487. The next prime is 21331537. The reversal of 21331523 is 32513312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21331523 - 2⁶ = 21331459 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21331495 and 21331504.

It is not a weakly prime, because it can be changed into another prime (21331543) 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, 10665761 + 10665762.

It is an arithmetic number, because the mean of its divisors is an integer number (10665762).

Almost surely, 2^21331523 is an apocalyptic number.

21331523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331523 is an equidigital number, since it uses as much as digits as its factorization.

21331523 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 540, while the sum is 20.

The square root of 21331523 is about 4618.6061750273. The cubic root of 21331523 is about 277.3366644244.

Adding to 21331523 its reverse (32513312), we get a palindrome (53844835).

The spelling of 21331523 in words is "twenty-one million, three hundred thirty-one thousand, five hundred twenty-three".