645913 has 4 divisors (see below), whose sum is σ = 652288. Its totient is φ = 639540.

The previous prime is 645907. The next prime is 645937. The reversal of 645913 is 319546.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 319546 = 2 ⋅159773.

It is a cyclic number.

It is not a de Polignac number, because 645913 - 2¹⁷ = 514841 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645973) 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, 3033 + ... + 3238.

It is an arithmetic number, because the mean of its divisors is an integer number (163072).

2⁶⁴⁵⁹¹³ is an apocalyptic number.

It is an amenable number.

645913 is a deficient number, since it is larger than the sum of its proper divisors (6375).

645913 is a wasteful number, since it uses less digits than its factorization.

645913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6374.

The product of its digits is 3240, while the sum is 28.

The square root of 645913 is about 803.6871281786. The cubic root of 645913 is about 86.4419738470.

It can be divided in two parts, 645 and 913, that multiplied together give a palindrome (588885).

The spelling of 645913 in words is "six hundred forty-five thousand, nine hundred thirteen".