21021203617 has 2 divisors, whose sum is σ = 21021203618. Its totient is φ = 21021203616.

The previous prime is 21021203573. The next prime is 21021203627. The reversal of 21021203617 is 71630212012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16047569041 + 4973634576 = 126679^2 + 70524^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021203617 - 2¹¹ = 21021201569 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21021203591 and 21021203600.

It is not a weakly prime, because it can be changed into another prime (21021203627) 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, 10510601808 + 10510601809.

It is an arithmetic number, because the mean of its divisors is an integer number (10510601809).

Almost surely, 2^21021203617 is an apocalyptic number.

It is an amenable number.

21021203617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021203617 is an equidigital number, since it uses as much as digits as its factorization.

21021203617 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 25.

Adding to 21021203617 its reverse (71630212012), we get a palindrome (92651415629).

The spelling of 21021203617 in words is "twenty-one billion, twenty-one million, two hundred three thousand, six hundred seventeen".