20728969 has 2 divisors, whose sum is σ = 20728970. Its totient is φ = 20728968.

The previous prime is 20728963. The next prime is 20728993. The reversal of 20728969 is 96982702.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19474569 + 1254400 = 4413^2 + 1120^2 .

It is a cyclic number.

It is not a de Polignac number, because 20728969 - 2¹¹ = 20726921 is a prime.

It is a super-2 number, since 2×20728969² = 859380311605922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20728963) by changing a digit.

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 as a sum of consecutive naturals, namely, 10364484 + 10364485.

It is an arithmetic number, because the mean of its divisors is an integer number (10364485).

Almost surely, 2^20728969 is an apocalyptic number.

It is an amenable number.

20728969 is a deficient number, since it is larger than the sum of its proper divisors (1).

20728969 is an equidigital number, since it uses as much as digits as its factorization.

20728969 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108864, while the sum is 43.

The square root of 20728969 is about 4552.9077521953. The cubic root of 20728969 is about 274.7003634455.

The spelling of 20728969 in words is "twenty million, seven hundred twenty-eight thousand, nine hundred sixty-nine".