21220220173 has 2 divisors, whose sum is σ = 21220220174. Its totient is φ = 21220220172.

The previous prime is 21220220159. The next prime is 21220220237. The reversal of 21220220173 is 37102202212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19842103044 + 1378117129 = 140862^2 + 37123^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220220173 - 2²⁵ = 21186665741 is a prime.

It is a super-2 number, since 2×21220220173² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21220220873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610110086 + 10610110087.

It is an arithmetic number, because the mean of its divisors is an integer number (10610110087).

Almost surely, 2^21220220173 is an apocalyptic number.

It is an amenable number.

21220220173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220220173 is an equidigital number, since it uses as much as digits as its factorization.

21220220173 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 672, while the sum is 22.

Adding to 21220220173 its reverse (37102202212), we get a palindrome (58322422385).

The spelling of 21220220173 in words is "twenty-one billion, two hundred twenty million, two hundred twenty thousand, one hundred seventy-three".