21005512144 has 20 divisors (see below), whose sum is σ = 41058344196. Its totient is φ = 10409810432.

The previous prime is 21005512139. The next prime is 21005512153. The reversal of 21005512144 is 44121550012.

It can be written as a sum of positive squares in 2 ways, for example, as 784672144 + 20220840000 = 28012^2 + 142200^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5807239 + ... + 5810854.

Almost surely, 2^21005512144 is an apocalyptic number.

It is an amenable number.

21005512144 is a deficient number, since it is larger than the sum of its proper divisors (20052832052).

21005512144 is a wasteful number, since it uses less digits than its factorization.

21005512144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11618214 (or 11618208 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 25.

The spelling of 21005512144 in words is "twenty-one billion, five million, five hundred twelve thousand, one hundred forty-four".