21000221205 has 8 divisors (see below), whose sum is σ = 33600353952. Its totient is φ = 11200117968.

The previous prime is 21000221189. The next prime is 21000221243. The reversal of 21000221205 is 50212200012.

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

It is not a de Polignac number, because 21000221205 - 2⁴ = 21000221189 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15), and also a Moran number because the ratio is a prime number: 1400014747 = 21000221205 / (2 + 1 + 0 + 0 + 0 + 2 + 2 + 1 + 2 + 0 + 5).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 700007359 + ... + 700007388.

It is an arithmetic number, because the mean of its divisors is an integer number (4200044244).

Almost surely, 2^21000221205 is an apocalyptic number.

It is an amenable number.

21000221205 is a deficient number, since it is larger than the sum of its proper divisors (12600132747).

21000221205 is a wasteful number, since it uses less digits than its factorization.

21000221205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1400014755.

The product of its (nonzero) digits is 80, while the sum is 15.

Adding to 21000221205 its reverse (50212200012), we get a palindrome (71212421217).

The spelling of 21000221205 in words is "twenty-one billion, two hundred twenty-one thousand, two hundred five".