21000068657 has 2 divisors, whose sum is σ = 21000068658. Its totient is φ = 21000068656.

The previous prime is 21000068581. The next prime is 21000068693. The reversal of 21000068657 is 75686000012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20667225121 + 332843536 = 143761^2 + 18244^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000068657 - 2¹⁶ = 21000003121 is a prime.

It is not a weakly prime, because it can be changed into another prime (21000068357) 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, 10500034328 + 10500034329.

It is an arithmetic number, because the mean of its divisors is an integer number (10500034329).

Almost surely, 2^21000068657 is an apocalyptic number.

It is an amenable number.

21000068657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000068657 is an equidigital number, since it uses as much as digits as its factorization.

21000068657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20160, while the sum is 35.

Adding to 21000068657 its reverse (75686000012), we get a palindrome (96686068669).

The spelling of 21000068657 in words is "twenty-one billion, sixty-eight thousand, six hundred fifty-seven".