645749 has 6 divisors (see below), whose sum is σ = 699426. Its totient is φ = 595920.

The previous prime is 645739. The next prime is 645751. The reversal of 645749 is 947546.

It can be written as a sum of positive squares in 3 ways, for example, as 34225 + 611524 = 185^2 + 782^2 .

It is not a de Polignac number, because 645749 - 2⁸ = 645493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645739) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1742 + ... + 2079.

It is an arithmetic number, because the mean of its divisors is an integer number (116571).

2⁶⁴⁵⁷⁴⁹ is an apocalyptic number.

It is an amenable number.

645749 is a deficient number, since it is larger than the sum of its proper divisors (53677).

645749 is a wasteful number, since it uses less digits than its factorization.

645749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3847 (or 3834 counting only the distinct ones).

The product of its digits is 30240, while the sum is 35.

The square root of 645749 is about 803.5850919473. The cubic root of 645749 is about 86.4346572354.

The spelling of 645749 in words is "six hundred forty-five thousand, seven hundred forty-nine".