51645 has 16 divisors (see below), whose sum is σ = 90432. Its totient is φ = 24960.

The previous prime is 51637. The next prime is 51647. The reversal of 51645 is 54615.

It is a happy number.

It is not a de Polignac number, because 51645 - 2³ = 51637 is a prime.

It is a Curzon number.

It is a nialpdrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9 + ... + 321.

It is an arithmetic number, because the mean of its divisors is an integer number (5652).

2⁵¹⁶⁴⁵ is an apocalyptic number.

51645 is a gapful number since it is divisible by the number (55) formed by its first and last digit.

It is an amenable number.

51645 is a deficient number, since it is larger than the sum of its proper divisors (38787).

51645 is a wasteful number, since it uses less digits than its factorization.

51645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332.

The product of its digits is 600, while the sum is 21.

The square root of 51645 is about 227.2553629730. The cubic root of 51645 is about 37.2399789869.

It can be divided in two parts, 516 and 45, that multiplied together give a triangular number (23220 = T₂₁₅).

The spelling of 51645 in words is "fifty-one thousand, six hundred forty-five".