19728121 has 16 divisors (see below), whose sum is σ = 23434240. Its totient is φ = 16251840.

The previous prime is 19728113. The next prime is 19728139. The reversal of 19728121 is 12182791.

It is a cyclic number.

It is not a de Polignac number, because 19728121 - 2³ = 19728113 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19728101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49495 + ... + 49891.

It is an arithmetic number, because the mean of its divisors is an integer number (1464640).

Almost surely, 2^19728121 is an apocalyptic number.

It is an amenable number.

19728121 is a deficient number, since it is larger than the sum of its proper divisors (3706119).

19728121 is a wasteful number, since it uses less digits than its factorization.

19728121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 664.

The product of its digits is 2016, while the sum is 31.

The square root of 19728121 is about 4441.6349467285. The cubic root of 19728121 is about 270.2061571359.

The spelling of 19728121 in words is "nineteen million, seven hundred twenty-eight thousand, one hundred twenty-one".