21657236617 has 2 divisors, whose sum is σ = 21657236618. Its totient is φ = 21657236616.

The previous prime is 21657236551. The next prime is 21657236633. The reversal of 21657236617 is 71663275612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17735846976 + 3921389641 = 133176^2 + 62621^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21657236617 is a prime.

It is not a weakly prime, because it can be changed into another prime (21657236017) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10828618308 + 10828618309.

It is an arithmetic number, because the mean of its divisors is an integer number (10828618309).

Almost surely, 2^21657236617 is an apocalyptic number.

It is an amenable number.

21657236617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21657236617 is an equidigital number, since it uses as much as digits as its factorization.

21657236617 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 635040, while the sum is 46.

The spelling of 21657236617 in words is "twenty-one billion, six hundred fifty-seven million, two hundred thirty-six thousand, six hundred seventeen".