645406 has 8 divisors (see below), whose sum is σ = 972144. Its totient is φ = 321360.

The previous prime is 645397. The next prime is 645409. The reversal of 645406 is 604546.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645409) by changing a digit.

645406 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, 111 + ... + 1141.

It is an arithmetic number, because the mean of its divisors is an integer number (121518).

2⁶⁴⁵⁴⁰⁶ is an apocalyptic number.

645406 is a deficient number, since it is larger than the sum of its proper divisors (326738).

645406 is a wasteful number, since it uses less digits than its factorization.

645406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1346.

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 645406 is about 803.3716450062. The cubic root of 645406 is about 86.4193508040.

It can be divided in two parts, 64540 and 6, that added together give a palindrome (64546).

The spelling of 645406 in words is "six hundred forty-five thousand, four hundred six".