20728139 has 2 divisors, whose sum is σ = 20728140. Its totient is φ = 20728138.

The previous prime is 20728133. The next prime is 20728153. The reversal of 20728139 is 93182702.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20728139 is a prime.

It is not a weakly prime, because it can be changed into another prime (20728133) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10364069 + 10364070.

It is an arithmetic number, because the mean of its divisors is an integer number (10364070).

Almost surely, 2^20728139 is an apocalyptic number.

20728139 is a deficient number, since it is larger than the sum of its proper divisors (1).

20728139 is an equidigital number, since it uses as much as digits as its factorization.

20728139 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 20728139 is about 4552.8166007429. The cubic root of 20728139 is about 274.6966970090.

The spelling of 20728139 in words is "twenty million, seven hundred twenty-eight thousand, one hundred thirty-nine".