21157607717 has 2 divisors, whose sum is σ = 21157607718. Its totient is φ = 21157607716.

The previous prime is 21157607677. The next prime is 21157607743. The reversal of 21157607717 is 71770675112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17357008516 + 3800599201 = 131746^2 + 61649^2 .

It is a cyclic number.

It is not a de Polignac number, because 21157607717 - 2¹⁶ = 21157542181 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21157607767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10578803858 + 10578803859.

It is an arithmetic number, because the mean of its divisors is an integer number (10578803859).

Almost surely, 2^21157607717 is an apocalyptic number.

It is an amenable number.

21157607717 is a deficient number, since it is larger than the sum of its proper divisors (1).

21157607717 is an equidigital number, since it uses as much as digits as its factorization.

21157607717 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144060, while the sum is 44.

The spelling of 21157607717 in words is "twenty-one billion, one hundred fifty-seven million, six hundred seven thousand, seven hundred seventeen".