645783 has 4 divisors (see below), whose sum is σ = 861048. Its totient is φ = 430520.

The previous prime is 645763. The next prime is 645787. The reversal of 645783 is 387546.

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 645783 - 2⁵ = 645751 is a prime.

It is a D-number.

645783 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107628 + ... + 107633.

It is an arithmetic number, because the mean of its divisors is an integer number (215262).

2⁶⁴⁵⁷⁸³ is an apocalyptic number.

645783 is a deficient number, since it is larger than the sum of its proper divisors (215265).

645783 is a wasteful number, since it uses less digits than its factorization.

645783 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215264.

The product of its digits is 20160, while the sum is 33.

The square root of 645783 is about 803.6062468647. The cubic root of 645783 is about 86.4361741957.

Adding to 645783 its sum of digits (33), we get a triangular number (645816 = T₁₁₃₆).

The spelling of 645783 in words is "six hundred forty-five thousand, seven hundred eighty-three".