21756075617 has 2 divisors, whose sum is σ = 21756075618. Its totient is φ = 21756075616.

The previous prime is 21756075611. The next prime is 21756075641. The reversal of 21756075617 is 71657065712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11546791936 + 10209283681 = 107456^2 + 101041^2 .

It is a cyclic number.

It is not a de Polignac number, because 21756075617 - 2¹⁸ = 21755813473 is a prime.

It is not a weakly prime, because it can be changed into another prime (21756075611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10878037808 + 10878037809.

It is an arithmetic number, because the mean of its divisors is an integer number (10878037809).

Almost surely, 2^21756075617 is an apocalyptic number.

It is an amenable number.

21756075617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21756075617 is an equidigital number, since it uses as much as digits as its factorization.

21756075617 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 617400, while the sum is 47.

The spelling of 21756075617 in words is "twenty-one billion, seven hundred fifty-six million, seventy-five thousand, six hundred seventeen".