21717204135257 has 2 divisors, whose sum is σ = 21717204135258. Its totient is φ = 21717204135256.

The previous prime is 21717204135233. The next prime is 21717204135271. The reversal of 21717204135257 is 75253140271712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13202620198681 + 8514583936576 = 3633541^2 + 2917976^2 .

It is a cyclic number.

It is not a de Polignac number, because 21717204135257 - 2¹⁴ = 21717204118873 is a prime.

It is not a weakly prime, because it can be changed into another prime (21717204135287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10858602067628 + 10858602067629.

It is an arithmetic number, because the mean of its divisors is an integer number (10858602067629).

Almost surely, 2^{21717204135257} is an apocalyptic number.

It is an amenable number.

21717204135257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21717204135257 is an equidigital number, since it uses as much as digits as its factorization.

21717204135257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 823200, while the sum is 47.

The spelling of 21717204135257 in words is "twenty-one trillion, seven hundred seventeen billion, two hundred four million, one hundred thirty-five thousand, two hundred fifty-seven".