21211020205 has 16 divisors (see below), whose sum is σ = 25888022784. Its totient is φ = 16681357440.

The previous prime is 21211020191. The next prime is 21211020269. The reversal of 21211020205 is 50202011212.

It is a happy number.

It is not a de Polignac number, because 21211020205 - 2⁹ = 21211019693 is a prime.

It is a Duffinian number.

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 15 ways as a sum of consecutive naturals, for example, 79761 + ... + 220870.

It is an arithmetic number, because the mean of its divisors is an integer number (1618001424).

Almost surely, 2^21211020205 is an apocalyptic number.

It is an amenable number.

21211020205 is a deficient number, since it is larger than the sum of its proper divisors (4677002579).

21211020205 is a wasteful number, since it uses less digits than its factorization.

21211020205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 300876.

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

Adding to 21211020205 its reverse (50202011212), we get a palindrome (71413031417).

The spelling of 21211020205 in words is "twenty-one billion, two hundred eleven million, twenty thousand, two hundred five".