20128034721555 has 64 divisors (see below), whose sum is σ = 36283246371840. Its totient is φ = 10585010016000.

The previous prime is 20128034721523. The next prime is 20128034721559. The reversal of 20128034721555 is 55512743082102.

20128034721555 is a `hidden beast` number, since 2 + 0 + 1 + 28 + 0 + 3 + 4 + 72 + 1 + 555 = 666.

It is not a de Polignac number, because 20128034721555 - 2⁵ = 20128034721523 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 20128034721555.

It is not an unprimeable number, because it can be changed into a prime (20128034721559) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 36098130 + ... + 36651480.

It is an arithmetic number, because the mean of its divisors is an integer number (566925724560).

Almost surely, 2^{20128034721555} is an apocalyptic number.

20128034721555 is a deficient number, since it is larger than the sum of its proper divisors (16155211650285).

20128034721555 is a wasteful number, since it uses less digits than its factorization.

20128034721555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 557129 (or 557123 counting only the distinct ones).

The product of its (nonzero) digits is 672000, while the sum is 45.

The spelling of 20128034721555 in words is "twenty trillion, one hundred twenty-eight billion, thirty-four million, seven hundred twenty-one thousand, five hundred fifty-five".