645550 has 12 divisors (see below), whose sum is σ = 1200816. Its totient is φ = 258200.

The previous prime is 645529. The next prime is 645571. The reversal of 645550 is 55546.

It is an interprime number because it is at equal distance from previous prime (645529) and next prime (645571).

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is an unprimeable number.

645550 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6406 + ... + 6505.

It is an arithmetic number, because the mean of its divisors is an integer number (100068).

2⁶⁴⁵⁵⁵⁰ is an apocalyptic number.

645550 is a deficient number, since it is larger than the sum of its proper divisors (555266).

645550 is a wasteful number, since it uses less digits than its factorization.

645550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12923 (or 12918 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 25.

The square root of 645550 is about 803.4612622896. The cubic root of 645550 is about 86.4257774880.

The spelling of 645550 in words is "six hundred forty-five thousand, five hundred fifty".