644667 has 8 divisors (see below), whose sum is σ = 897024. Its totient is φ = 411048.

The previous prime is 644653. The next prime is 644669. The reversal of 644667 is 766446.

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

It is not a de Polignac number, because 644667 - 2⁸ = 644411 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4603 + ... + 4740.

It is an arithmetic number, because the mean of its divisors is an integer number (112128).

2⁶⁴⁴⁶⁶⁷ is an apocalyptic number.

644667 is a deficient number, since it is larger than the sum of its proper divisors (252357).

644667 is a wasteful number, since it uses less digits than its factorization.

644667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9369.

The product of its digits is 24192, while the sum is 33.

The square root of 644667 is about 802.9115767007. The cubic root of 644667 is about 86.3863543693.

The spelling of 644667 in words is "six hundred forty-four thousand, six hundred sixty-seven".