19720728 has 24 divisors (see below), whose sum is σ = 53410500. Its totient is φ = 6573552.

The previous prime is 19720699. The next prime is 19720733. The reversal of 19720728 is 82702791.

It is a tau number, because it is divible by the number of its divisors (24).

It is a super-2 number, since 2×19720728² = 777814225699968, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 19720692 and 19720701.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 136878 + ... + 137021.

Almost surely, 2^19720728 is an apocalyptic number.

19720728 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

19720728 is an abundant number, since it is smaller than the sum of its proper divisors (33689772).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

19720728 is a wasteful number, since it uses less digits than its factorization.

19720728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 273911 (or 273904 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The square root of 19720728 is about 4440.8026301559. The cubic root of 19720728 is about 270.1724001838.

The spelling of 19720728 in words is "nineteen million, seven hundred twenty thousand, seven hundred twenty-eight".