645547 has 4 divisors (see below), whose sum is σ = 737776. Its totient is φ = 553320.

The previous prime is 645529. The next prime is 645571. The reversal of 645547 is 745546.

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: 745546 = 2 ⋅372773.

It is a cyclic number.

It is not a de Polignac number, because 645547 - 2⁷ = 645419 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645527) 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, 46104 + ... + 46117.

It is an arithmetic number, because the mean of its divisors is an integer number (184444).

2⁶⁴⁵⁵⁴⁷ is an apocalyptic number.

645547 is a deficient number, since it is larger than the sum of its proper divisors (92229).

645547 is an equidigital number, since it uses as much as digits as its factorization.

645547 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92228.

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

The square root of 645547 is about 803.4593953648. The cubic root of 645547 is about 86.4256436085.

Subtracting 645547 from its reverse (745546), we obtain a palindrome (99999).

The spelling of 645547 in words is "six hundred forty-five thousand, five hundred forty-seven".