20421728 has 12 divisors (see below), whose sum is σ = 40205340. Its totient is φ = 10210848.

The previous prime is 20421719. The next prime is 20421733. The reversal of 20421728 is 82712402.

It is a junction number, because it is equal to n+sod(n) for n = 20421697 and 20421706.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319058 + ... + 319121.

It is an arithmetic number, because the mean of its divisors is an integer number (3350445).

Almost surely, 2^20421728 is an apocalyptic number.

It is an amenable number.

20421728 is a deficient number, since it is larger than the sum of its proper divisors (19783612).

20421728 is an equidigital number, since it uses as much as digits as its factorization.

20421728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 638189 (or 638181 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 26.

The square root of 20421728 is about 4519.0406061464. The cubic root of 20421728 is about 273.3364161196.

The spelling of 20421728 in words is "twenty million, four hundred twenty-one thousand, seven hundred twenty-eight".