21129728245 has 16 divisors (see below), whose sum is σ = 25439554800. Its totient is φ = 16847921664.

The previous prime is 21129728177. The next prime is 21129728299. The reversal of 21129728245 is 54282792112.

It can be written as a sum of positive squares in 8 ways, for example, as 5604319044 + 15525409201 = 74862^2 + 124601^2 .

It is a cyclic number.

It is not a de Polignac number, because 21129728245 - 2⁷ = 21129728117 is a prime.

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, 4542681 + ... + 4547329.

It is an arithmetic number, because the mean of its divisors is an integer number (1589972175).

Almost surely, 2^21129728245 is an apocalyptic number.

It is an amenable number.

21129728245 is a deficient number, since it is larger than the sum of its proper divisors (4309826555).

21129728245 is a wasteful number, since it uses less digits than its factorization.

21129728245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7464.

The product of its digits is 161280, while the sum is 43.

The spelling of 21129728245 in words is "twenty-one billion, one hundred twenty-nine million, seven hundred twenty-eight thousand, two hundred forty-five".