20728639 has 8 divisors (see below), whose sum is σ = 22022000. Its totient is φ = 19455552.

The previous prime is 20728637. The next prime is 20728691. The reversal of 20728639 is 93682702.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20728639 - 2¹ = 20728637 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20728598 and 20728607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20728633) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2934 + ... + 7075.

It is an arithmetic number, because the mean of its divisors is an integer number (2752750).

Almost surely, 2^20728639 is an apocalyptic number.

20728639 is a deficient number, since it is larger than the sum of its proper divisors (1293361).

20728639 is a wasteful number, since it uses less digits than its factorization.

20728639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10137.

The product of its (nonzero) digits is 36288, while the sum is 37.

The square root of 20728639 is about 4552.8715114749. The cubic root of 20728639 is about 274.6989057174.

The spelling of 20728639 in words is "twenty million, seven hundred twenty-eight thousand, six hundred thirty-nine".