21820008505 has 8 divisors (see below), whose sum is σ = 26184990600. Its totient is φ = 17455353216.

The previous prime is 21820008499. The next prime is 21820008517. The reversal of 21820008505 is 50580002812.

It can be written as a sum of positive squares in 4 ways, for example, as 5149067049 + 16670941456 = 71757^2 + 129116^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21820008505 - 2⁷ = 21820008377 is a prime.

It is a super-2 number, since 2×21820008505² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 103261 + ... + 233029.

It is an arithmetic number, because the mean of its divisors is an integer number (3273123825).

Almost surely, 2^21820008505 is an apocalyptic number.

It is an amenable number.

21820008505 is a deficient number, since it is larger than the sum of its proper divisors (4364982095).

21820008505 is a wasteful number, since it uses less digits than its factorization.

21820008505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163403.

The product of its (nonzero) digits is 6400, while the sum is 31.

The spelling of 21820008505 in words is "twenty-one billion, eight hundred twenty million, eight thousand, five hundred five".