645331 has 4 divisors (see below), whose sum is σ = 648000. Its totient is φ = 642664.

The previous prime is 645329. The next prime is 645347. The reversal of 645331 is 133546.

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 645331 - 2¹ = 645329 is a prime.

It is a super-2 number, since 2×645331² = 832904199122, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (645131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 931 + ... + 1468.

It is an arithmetic number, because the mean of its divisors is an integer number (162000).

2⁶⁴⁵³³¹ is an apocalyptic number.

645331 is a deficient number, since it is larger than the sum of its proper divisors (2669).

645331 is a wasteful number, since it uses less digits than its factorization.

645331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2668.

The product of its digits is 1080, while the sum is 22.

The square root of 645331 is about 803.3249653783. The cubic root of 645331 is about 86.4160031942.

Adding to 645331 its reverse (133546), we get a palindrome (778877).

The spelling of 645331 in words is "six hundred forty-five thousand, three hundred thirty-one".