21756020617 has 2 divisors, whose sum is σ = 21756020618. Its totient is φ = 21756020616.

The previous prime is 21756020599. The next prime is 21756020621. The reversal of 21756020617 is 71602065712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21158902521 + 597118096 = 145461^2 + 24436^2 .

It is a cyclic number.

It is not a de Polignac number, because 21756020617 - 2¹¹ = 21756018569 is a prime.

It is a super-3 number, since 3×21756020617³ (a number of 32 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21756020677) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10878010308 + 10878010309.

It is an arithmetic number, because the mean of its divisors is an integer number (10878010309).

Almost surely, 2^21756020617 is an apocalyptic number.

It is an amenable number.

21756020617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21756020617 is an equidigital number, since it uses as much as digits as its factorization.

21756020617 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 35280, while the sum is 37.

The spelling of 21756020617 in words is "twenty-one billion, seven hundred fifty-six million, twenty thousand, six hundred seventeen".