21516304005257 has 2 divisors, whose sum is σ = 21516304005258. Its totient is φ = 21516304005256.

The previous prime is 21516304005199. The next prime is 21516304005263. The reversal of 21516304005257 is 75250040361512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20487355479616 + 1028948525641 = 4526296^2 + 1014371^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21516304005257 is a prime.

It is not a weakly prime, because it can be changed into another prime (21516304035257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758152002628 + 10758152002629.

It is an arithmetic number, because the mean of its divisors is an integer number (10758152002629).

Almost surely, 2^{21516304005257} is an apocalyptic number.

It is an amenable number.

21516304005257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21516304005257 is an equidigital number, since it uses as much as digits as its factorization.

21516304005257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 252000, while the sum is 41.

Adding to 21516304005257 its reverse (75250040361512), we get a palindrome (96766344366769).

The spelling of 21516304005257 in words is "twenty-one trillion, five hundred sixteen billion, three hundred four million, five thousand, two hundred fifty-seven".