20731305 has 16 divisors (see below), whose sum is σ = 37908864. Its totient is φ = 9477120.

The previous prime is 20731301. The next prime is 20731307. The reversal of 20731305 is 50313702.

It is a happy number.

It is not a de Polignac number, because 20731305 - 2² = 20731301 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20731301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 98616 + ... + 98825.

It is an arithmetic number, because the mean of its divisors is an integer number (2369304).

Almost surely, 2^20731305 is an apocalyptic number.

It is an amenable number.

20731305 is a deficient number, since it is larger than the sum of its proper divisors (17177559).

20731305 is a wasteful number, since it uses less digits than its factorization.

20731305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 197456.

The product of its (nonzero) digits is 630, while the sum is 21.

The square root of 20731305 is about 4553.1642843192. The cubic root of 20731305 is about 274.7106819511.

The spelling of 20731305 in words is "twenty million, seven hundred thirty-one thousand, three hundred five".