20151 has 6 divisors (see below), whose sum is σ = 29120. Its totient is φ = 13428.

The previous prime is 20149. The next prime is 20161. The reversal of 20151 is 15102.

It is a happy number.

It is not a de Polignac number, because 20151 - 2¹ = 20149 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 2239 = 20151 / (2 + 0 + 1 + 5 + 1).

It is a Duffinian number.

20151 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20101) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1111 + ... + 1128.

2²⁰¹⁵¹ is an apocalyptic number.

20151 is a deficient number, since it is larger than the sum of its proper divisors (8969).

20151 is a wasteful number, since it uses less digits than its factorization.

20151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2245 (or 2242 counting only the distinct ones).

The product of its (nonzero) digits is 10, while the sum is 9.

The square root of 20151 is about 141.9542179719. The cubic root of 20151 is about 27.2123178061.

Adding to 20151 its reverse (15102), we get a palindrome (35253).

It can be divided in two parts, 2015 and 1, that added together give a triangular number (2016 = T₆₃).

The spelling of 20151 in words is "twenty thousand, one hundred fifty-one".