644947 has 4 divisors (see below), whose sum is σ = 662416. Its totient is φ = 627480.

The previous prime is 644933. The next prime is 644951. The reversal of 644947 is 749446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644947 - 2¹¹ = 642899 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644977) 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, 8679 + ... + 8752.

It is an arithmetic number, because the mean of its divisors is an integer number (165604).

2⁶⁴⁴⁹⁴⁷ is an apocalyptic number.

644947 is a deficient number, since it is larger than the sum of its proper divisors (17469).

644947 is a wasteful number, since it uses less digits than its factorization.

644947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17468.

The product of its digits is 24192, while the sum is 34.

The square root of 644947 is about 803.0859231739. The cubic root of 644947 is about 86.3988593671.

The spelling of 644947 in words is "six hundred forty-four thousand, nine hundred forty-seven".