645278 has 8 divisors (see below), whose sum is σ = 1018920. Its totient is φ = 305640.

The previous prime is 645257. The next prime is 645313. The reversal of 645278 is 872546.

Added to its reverse (872546) it gives a square (1517824 = 1232²).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

645278 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 8453 + ... + 8528.

It is an arithmetic number, because the mean of its divisors is an integer number (127365).

2⁶⁴⁵²⁷⁸ is an apocalyptic number.

645278 is a deficient number, since it is larger than the sum of its proper divisors (373642).

645278 is a wasteful number, since it uses less digits than its factorization.

645278 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17002.

The product of its digits is 13440, while the sum is 32.

The square root of 645278 is about 803.2919768054. The cubic root of 645278 is about 86.4136373935.

Adding to 645278 its reverse (872546), we get a square (1517824 = 1232²).

The spelling of 645278 in words is "six hundred forty-five thousand, two hundred seventy-eight".