645543 has 8 divisors (see below), whose sum is σ = 956400. Its totient is φ = 430344.

The previous prime is 645529. The next prime is 645571. The reversal of 645543 is 345546.

It is not a de Polignac number, because 645543 - 2⁴ = 645527 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 23909 = 645543 / (6 + 4 + 5 + 5 + 4 + 3).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645503) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11928 + ... + 11981.

It is an arithmetic number, because the mean of its divisors is an integer number (119550).

2⁶⁴⁵⁵⁴³ is an apocalyptic number.

645543 is a deficient number, since it is larger than the sum of its proper divisors (310857).

645543 is a wasteful number, since it uses less digits than its factorization.

645543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23918 (or 23912 counting only the distinct ones).

The product of its digits is 7200, while the sum is 27.

The square root of 645543 is about 803.4569061250. The cubic root of 645543 is about 86.4254651018.

The spelling of 645543 in words is "six hundred forty-five thousand, five hundred forty-three".