20457 has 6 divisors (see below), whose sum is σ = 29562. Its totient is φ = 13632.

The previous prime is 20443. The next prime is 20477. The reversal of 20457 is 75402.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 19881 + 576 = 141^2 + 24^2 .

It is not a de Polignac number, because 20457 - 2⁴ = 20441 is a prime.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20407) 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, 1128 + ... + 1145.

It is an arithmetic number, because the mean of its divisors is an integer number (4927).

2²⁰⁴⁵⁷ is an apocalyptic number.

It is an amenable number.

20457 is a deficient number, since it is larger than the sum of its proper divisors (9105).

20457 is a wasteful number, since it uses less digits than its factorization.

20457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2279 (or 2276 counting only the distinct ones).

The product of its (nonzero) digits is 280, while the sum is 18.

The square root of 20457 is about 143.0279692927. The cubic root of 20457 is about 27.3493692669.

Adding to 20457 its reverse (75402), we get a palindrome (95859).

Subtracting 20457 from its reverse (75402), we obtain a palindrome (54945).

It can be divided in two parts, 204 and 57, that multiplied together give a triangular number (11628 = T₁₅₂).

The spelling of 20457 in words is "twenty thousand, four hundred fifty-seven".