20731 has 2 divisors, whose sum is σ = 20732. Its totient is φ = 20730.

The previous prime is 20719. The next prime is 20743. The reversal of 20731 is 13702.

It is a balanced prime because it is at equal distance from previous prime (20719) and next prime (20743).

It is a cyclic number.

It is not a de Polignac number, because 20731 - 2⁹ = 20219 is a prime.

It is a super-2 number, since 2×20731² = 859548722, which contains 22 as substring.

It is a Chen prime.

20731 is a lucky number.

It is a plaindrome in base 14.

It is a nialpdrome in base 12 and base 15.

It is not a weakly prime, because it can be changed into another prime (20771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10365 + 10366.

It is an arithmetic number, because the mean of its divisors is an integer number (10366).

2²⁰⁷³¹ is an apocalyptic number.

20731 is a deficient number, since it is larger than the sum of its proper divisors (1).

20731 is an equidigital number, since it uses as much as digits as its factorization.

20731 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42, while the sum is 13.

The square root of 20731 is about 143.9826378422. The cubic root of 20731 is about 27.4709334759.

The spelling of 20731 in words is "twenty thousand, seven hundred thirty-one".