21006353617 has 2 divisors, whose sum is σ = 21006353618. Its totient is φ = 21006353616.

The previous prime is 21006353591. The next prime is 21006353623. The reversal of 21006353617 is 71635360012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11212480321 + 9793873296 = 105889^2 + 98964^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21006353617 is a prime.

It is not a weakly prime, because it can be changed into another prime (21006351617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503176808 + 10503176809.

It is an arithmetic number, because the mean of its divisors is an integer number (10503176809).

Almost surely, 2^21006353617 is an apocalyptic number.

It is an amenable number.

21006353617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21006353617 is an equidigital number, since it uses as much as digits as its factorization.

21006353617 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 22680, while the sum is 34.

The spelling of 21006353617 in words is "twenty-one billion, six million, three hundred fifty-three thousand, six hundred seventeen".