21324257 has 2 divisors, whose sum is σ = 21324258. Its totient is φ = 21324256.

The previous prime is 21324253. The next prime is 21324263. The reversal of 21324257 is 75242312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15178816 + 6145441 = 3896^2 + 2479^2 .

It is a cyclic number.

It is not a de Polignac number, because 21324257 - 2² = 21324253 is a prime.

It is not a weakly prime, because it can be changed into another prime (21324253) 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 as a sum of consecutive naturals, namely, 10662128 + 10662129.

It is an arithmetic number, because the mean of its divisors is an integer number (10662129).

Almost surely, 2^21324257 is an apocalyptic number.

It is an amenable number.

21324257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21324257 is an equidigital number, since it uses as much as digits as its factorization.

21324257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3360, while the sum is 26.

The square root of 21324257 is about 4617.8195070834. The cubic root of 21324257 is about 277.3051717981.

Adding to 21324257 its reverse (75242312), we get a palindrome (96566569).

The spelling of 21324257 in words is "twenty-one million, three hundred twenty-four thousand, two hundred fifty-seven".