21002001217 has 2 divisors, whose sum is σ = 21002001218. Its totient is φ = 21002001216.

The previous prime is 21002001203. The next prime is 21002001221. The reversal of 21002001217 is 71210020012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15525409201 + 5476592016 = 124601^2 + 74004^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21002001217 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21002001217.

It is not a weakly prime, because it can be changed into another prime (21002001817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501000608 + 10501000609.

It is an arithmetic number, because the mean of its divisors is an integer number (10501000609).

Almost surely, 2^21002001217 is an apocalyptic number.

It is an amenable number.

21002001217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002001217 is an equidigital number, since it uses as much as digits as its factorization.

21002001217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 56, while the sum is 16.

Adding to 21002001217 its reverse (71210020012), we get a palindrome (92212021229).

The spelling of 21002001217 in words is "twenty-one billion, two million, one thousand, two hundred seventeen".