20351 has 4 divisors (see below), whose sum is σ = 20832. Its totient is φ = 19872.

The previous prime is 20347. The next prime is 20353. The reversal of 20351 is 15302.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20351 - 2² = 20347 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 20351.

It is not an unprimeable number, because it can be changed into a prime (20353) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 170 + ... + 263.

It is an arithmetic number, because the mean of its divisors is an integer number (5208).

2²⁰³⁵¹ is an apocalyptic number.

20351 is a deficient number, since it is larger than the sum of its proper divisors (481).

20351 is an equidigital number, since it uses as much as digits as its factorization.

20351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480.

The product of its (nonzero) digits is 30, while the sum is 11.

The square root of 20351 is about 142.6569311320. The cubic root of 20351 is about 27.3020496075.

Adding to 20351 its reverse (15302), we get a palindrome (35653).

The spelling of 20351 in words is "twenty thousand, three hundred fifty-one".