21365303257 has 2 divisors, whose sum is σ = 21365303258. Its totient is φ = 21365303256.

The previous prime is 21365303249. The next prime is 21365303263. The reversal of 21365303257 is 75230356312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11790485056 + 9574818201 = 108584^2 + 97851^2 .

It is a cyclic number.

It is not a de Polignac number, because 21365303257 - 2³ = 21365303249 is a prime.

It is not a weakly prime, because it can be changed into another prime (21365303227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10682651628 + 10682651629.

It is an arithmetic number, because the mean of its divisors is an integer number (10682651629).

Almost surely, 2^21365303257 is an apocalyptic number.

It is an amenable number.

21365303257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21365303257 is an equidigital number, since it uses as much as digits as its factorization.

21365303257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 113400, while the sum is 37.

Adding to 21365303257 its reverse (75230356312), we get a palindrome (96595659569).

The spelling of 21365303257 in words is "twenty-one billion, three hundred sixty-five million, three hundred three thousand, two hundred fifty-seven".