21312523 has 2 divisors, whose sum is σ = 21312524. Its totient is φ = 21312522.

The previous prime is 21312517. The next prime is 21312539. The reversal of 21312523 is 32521312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21312523 - 2¹⁷ = 21181451 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21312523.

It is not a weakly prime, because it can be changed into another prime (21312023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656261 + 10656262.

It is an arithmetic number, because the mean of its divisors is an integer number (10656262).

Almost surely, 2^21312523 is an apocalyptic number.

21312523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312523 is an equidigital number, since it uses as much as digits as its factorization.

21312523 is an evil number, because the sum of its binary digits is even.

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

The square root of 21312523 is about 4616.5488191938. The cubic root of 21312523 is about 277.2542986555.

Adding to 21312523 its reverse (32521312), we get a palindrome (53833835).

The spelling of 21312523 in words is "twenty-one million, three hundred twelve thousand, five hundred twenty-three".