21981152617 has 2 divisors, whose sum is σ = 21981152618. Its totient is φ = 21981152616.

The previous prime is 21981152603. The next prime is 21981152639. The reversal of 21981152617 is 71625118912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17768623401 + 4212529216 = 133299^2 + 64904^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21981152617 is a prime.

It is not a weakly prime, because it can be changed into another prime (21981152657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10990576308 + 10990576309.

It is an arithmetic number, because the mean of its divisors is an integer number (10990576309).

Almost surely, 2^21981152617 is an apocalyptic number.

It is an amenable number.

21981152617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21981152617 is an equidigital number, since it uses as much as digits as its factorization.

21981152617 is an evil number, because the sum of its binary digits is even.

The product of its digits is 60480, while the sum is 43.

The spelling of 21981152617 in words is "twenty-one billion, nine hundred eighty-one million, one hundred fifty-two thousand, six hundred seventeen".