21231020017 has 2 divisors, whose sum is σ = 21231020018. Its totient is φ = 21231020016.

The previous prime is 21231020009. The next prime is 21231020047. The reversal of 21231020017 is 71002013212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14188621456 + 7042398561 = 119116^2 + 83919^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231020017 - 2³ = 21231020009 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21231019976 and 21231020003.

It is not a weakly prime, because it can be changed into another prime (21231020047) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615510008 + 10615510009.

It is an arithmetic number, because the mean of its divisors is an integer number (10615510009).

Almost surely, 2^21231020017 is an apocalyptic number.

It is an amenable number.

21231020017 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231020017 is an equidigital number, since it uses as much as digits as its factorization.

21231020017 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 168, while the sum is 19.

Adding to 21231020017 its reverse (71002013212), we get a palindrome (92233033229).

The spelling of 21231020017 in words is "twenty-one billion, two hundred thirty-one million, twenty thousand, seventeen".