21201221005 has 16 divisors (see below), whose sum is σ = 26621927424. Its totient is φ = 16188992640.

The previous prime is 21201220981. The next prime is 21201221021. The reversal of 21201221005 is 50012210212.

It is a happy number.

It is not a de Polignac number, because 21201221005 - 2⁹ = 21201220493 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21201221005.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 925549 + ... + 948178.

It is an arithmetic number, because the mean of its divisors is an integer number (1663870464).

Almost surely, 2^21201221005 is an apocalyptic number.

It is an amenable number.

21201221005 is a deficient number, since it is larger than the sum of its proper divisors (5420706419).

21201221005 is a wasteful number, since it uses less digits than its factorization.

21201221005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1873836.

The product of its (nonzero) digits is 80, while the sum is 16.

Adding to 21201221005 its reverse (50012210212), we get a palindrome (71213431217).

The spelling of 21201221005 in words is "twenty-one billion, two hundred one million, two hundred twenty-one thousand, five".