21021020117 has 2 divisors, whose sum is σ = 21021020118. Its totient is φ = 21021020116.

The previous prime is 21021020099. The next prime is 21021020159. The reversal of 21021020117 is 71102012012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20139583396 + 881436721 = 141914^2 + 29689^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021020117 - 2¹⁴ = 21021003733 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21021020095 and 21021020104.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21021050117) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510510058 + 10510510059.

It is an arithmetic number, because the mean of its divisors is an integer number (10510510059).

Almost surely, 2^21021020117 is an apocalyptic number.

It is an amenable number.

21021020117 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021020117 is an equidigital number, since it uses as much as digits as its factorization.

21021020117 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 56, while the sum is 17.

Adding to 21021020117 its reverse (71102012012), we get a palindrome (92123032129).

The spelling of 21021020117 in words is "twenty-one billion, twenty-one million, twenty thousand, one hundred seventeen".