21810021005 has 16 divisors (see below), whose sum is σ = 26284532400. Its totient is φ = 17373089280.

The previous prime is 21810020983. The next prime is 21810021019. The reversal of 21810021005 is 50012001812.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 4676781769 + 17133239236 = 68387^2 + 130894^2 .

It is not a de Polignac number, because 21810021005 - 2²² = 21805826701 is a prime.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 3064391 + ... + 3071499.

It is an arithmetic number, because the mean of its divisors is an integer number (1642783275).

Almost surely, 2^21810021005 is an apocalyptic number.

It is an amenable number.

21810021005 is a deficient number, since it is larger than the sum of its proper divisors (4474511395).

21810021005 is a wasteful number, since it uses less digits than its factorization.

21810021005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9664.

The product of its (nonzero) digits is 160, while the sum is 20.

Adding to 21810021005 its reverse (50012001812), we get a palindrome (71822022817).

The spelling of 21810021005 in words is "twenty-one billion, eight hundred ten million, twenty-one thousand, five".