21125204205 has 128 divisors (see below), whose sum is σ = 40564592640. Its totient is φ = 9187706880.

The previous prime is 21125204147. The next prime is 21125204249. The reversal of 21125204205 is 50240252112.

It is not a de Polignac number, because 21125204205 - 2⁸ = 21125203949 is a prime.

It is a Curzon number.

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 127 ways as a sum of consecutive naturals, for example, 36996570 + ... + 36997140.

It is an arithmetic number, because the mean of its divisors is an integer number (316910880).

Almost surely, 2^21125204205 is an apocalyptic number.

It is an amenable number.

21125204205 is a deficient number, since it is larger than the sum of its proper divisors (19439388435).

21125204205 is a wasteful number, since it uses less digits than its factorization.

21125204205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 819.

The product of its (nonzero) digits is 1600, while the sum is 24.

Adding to 21125204205 its reverse (50240252112), we get a palindrome (71365456317).

The spelling of 21125204205 in words is "twenty-one billion, one hundred twenty-five million, two hundred four thousand, two hundred five".