20615729 has 2 divisors, whose sum is σ = 20615730. Its totient is φ = 20615728.

The previous prime is 20615671. The next prime is 20615731. The reversal of 20615729 is 92751602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17447329 + 3168400 = 4177^2 + 1780^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20615729 is a prime.

Together with 20615731, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 20615695 and 20615704.

It is not a weakly prime, because it can be changed into another prime (20615629) 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, 10307864 + 10307865.

It is an arithmetic number, because the mean of its divisors is an integer number (10307865).

Almost surely, 2^20615729 is an apocalyptic number.

It is an amenable number.

20615729 is a deficient number, since it is larger than the sum of its proper divisors (1).

20615729 is an equidigital number, since it uses as much as digits as its factorization.

20615729 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7560, while the sum is 32.

The square root of 20615729 is about 4540.4547129115. The cubic root of 20615729 is about 274.1992308439.

The spelling of 20615729 in words is "twenty million, six hundred fifteen thousand, seven hundred twenty-nine".