20405729 has 8 divisors (see below), whose sum is σ = 21649320. Its totient is φ = 19166976.

The previous prime is 20405713. The next prime is 20405743. The reversal of 20405729 is 92750402.

It can be written as a sum of positive squares in 4 ways, for example, as 1500625 + 18905104 = 1225^2 + 4348^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20405729 - 2⁴ = 20405713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20405789) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11207 + ... + 12899.

It is an arithmetic number, because the mean of its divisors is an integer number (2706165).

Almost surely, 2^20405729 is an apocalyptic number.

It is an amenable number.

20405729 is a deficient number, since it is larger than the sum of its proper divisors (1243591).

20405729 is a wasteful number, since it uses less digits than its factorization.

20405729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2419.

The product of its (nonzero) digits is 5040, while the sum is 29.

The square root of 20405729 is about 4517.2700826938. The cubic root of 20405729 is about 273.2650174631.

The spelling of 20405729 in words is "twenty million, four hundred five thousand, seven hundred twenty-nine".