20505731 has 8 divisors (see below), whose sum is σ = 21846720. Its totient is φ = 19190952.

The previous prime is 20505713. The next prime is 20505761. The reversal of 20505731 is 13750502.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20505731 is a prime.

It is a super-2 number, since 2×20505731² = 840970007688722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20505697 and 20505706.

It is not an unprimeable number, because it can be changed into a prime (20505761) 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 in 7 ways as a sum of consecutive naturals, for example, 4925 + ... + 8078.

It is an arithmetic number, because the mean of its divisors is an integer number (2730840).

Almost surely, 2^20505731 is an apocalyptic number.

20505731 is a deficient number, since it is larger than the sum of its proper divisors (1340989).

20505731 is a wasteful number, since it uses less digits than its factorization.

20505731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13105.

The product of its (nonzero) digits is 1050, while the sum is 23.

The square root of 20505731 is about 4528.3254079185. The cubic root of 20505731 is about 273.7106852627.

The spelling of 20505731 in words is "twenty million, five hundred five thousand, seven hundred thirty-one".