20728439 has 2 divisors, whose sum is σ = 20728440. Its totient is φ = 20728438.

The previous prime is 20728427. The next prime is 20728447. The reversal of 20728439 is 93482702.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20728439 - 2¹⁶ = 20662903 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 20728399 and 20728408.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20728469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10364219 + 10364220.

It is an arithmetic number, because the mean of its divisors is an integer number (10364220).

Almost surely, 2^20728439 is an apocalyptic number.

20728439 is a deficient number, since it is larger than the sum of its proper divisors (1).

20728439 is an equidigital number, since it uses as much as digits as its factorization.

20728439 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24192, while the sum is 35.

The square root of 20728439 is about 4552.8495472616. The cubic root of 20728439 is about 274.6980222383.

The spelling of 20728439 in words is "twenty million, seven hundred twenty-eight thousand, four hundred thirty-nine".