21516304035257 has 2 divisors, whose sum is σ = 21516304035258. Its totient is φ = 21516304035256.

The previous prime is 21516304035223. The next prime is 21516304035263. The reversal of 21516304035257 is 75253040361512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15984451779136 + 5531852256121 = 3998056^2 + 2351989^2 .

It is a cyclic number.

It is not a de Polignac number, because 21516304035257 - 2⁸ = 21516304035001 is a prime.

It is a super-2 number, since 2×21516304035257² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21516304005257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758152017628 + 10758152017629.

It is an arithmetic number, because the mean of its divisors is an integer number (10758152017629).

Almost surely, 2^{21516304035257} is an apocalyptic number.

It is an amenable number.

21516304035257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21516304035257 is an equidigital number, since it uses as much as digits as its factorization.

21516304035257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 756000, while the sum is 44.

Adding to 21516304035257 its reverse (75253040361512), we get a palindrome (96769344396769).

The spelling of 21516304035257 in words is "twenty-one trillion, five hundred sixteen billion, three hundred four million, thirty-five thousand, two hundred fifty-seven".