21553250317 has 2 divisors, whose sum is σ = 21553250318. Its totient is φ = 21553250316.

The previous prime is 21553250281. The next prime is 21553250321. The reversal of 21553250317 is 71305235512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20814987076 + 738263241 = 144274^2 + 27171^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21553250317 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21553250347) 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, 10776625158 + 10776625159.

It is an arithmetic number, because the mean of its divisors is an integer number (10776625159).

Almost surely, 2^21553250317 is an apocalyptic number.

It is an amenable number.

21553250317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21553250317 is an equidigital number, since it uses as much as digits as its factorization.

21553250317 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31500, while the sum is 34.

Adding to 21553250317 its reverse (71305235512), we get a palindrome (92858485829).

The spelling of 21553250317 in words is "twenty-one billion, five hundred fifty-three million, two hundred fifty thousand, three hundred seventeen".