21010423205 has 4 divisors (see below), whose sum is σ = 25212507852. Its totient is φ = 16808338560.

The previous prime is 21010423201. The next prime is 21010423243. The reversal of 21010423205 is 50232401012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3191911009 + 17818512196 = 56497^2 + 133486^2 .

It is not a de Polignac number, because 21010423205 - 2² = 21010423201 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010423201) 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 in 3 ways as a sum of consecutive naturals, for example, 2101042316 + ... + 2101042325.

It is an arithmetic number, because the mean of its divisors is an integer number (6303126963).

Almost surely, 2^21010423205 is an apocalyptic number.

It is an amenable number.

21010423205 is a deficient number, since it is larger than the sum of its proper divisors (4202084647).

21010423205 is an equidigital number, since it uses as much as digits as its factorization.

21010423205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4202084646.

The product of its (nonzero) digits is 480, while the sum is 20.

Adding to 21010423205 its reverse (50232401012), we get a palindrome (71242824217).

The spelling of 21010423205 in words is "twenty-one billion, ten million, four hundred twenty-three thousand, two hundred five".