645754 has 4 divisors (see below), whose sum is σ = 968634. Its totient is φ = 322876.

The previous prime is 645751. The next prime is 645763. The reversal of 645754 is 457546.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 457546 = 2 ⋅228773.

It can be written as a sum of positive squares in only one way, i.e., 603729 + 42025 = 777^2 + 205^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (645751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161437 + ... + 161440.

2⁶⁴⁵⁷⁵⁴ is an apocalyptic number.

645754 is a deficient number, since it is larger than the sum of its proper divisors (322880).

645754 is a wasteful number, since it uses less digits than its factorization.

645754 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322879.

The product of its digits is 16800, while the sum is 31.

The square root of 645754 is about 803.5882029995. The cubic root of 645754 is about 86.4348803211.

The spelling of 645754 in words is "six hundred forty-five thousand, seven hundred fifty-four".