644966 has 16 divisors (see below), whose sum is σ = 1154304. Its totient is φ = 264264.

The previous prime is 644951. The next prime is 644977. The reversal of 644966 is 669446.

It is a super-2 number, since 2×644966² = 831962282312, which contains 22 as substring.

644966 is a modest number, since divided by 966 gives 644 as remainder.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

644966 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 7 ways as a sum of consecutive naturals, for example, 680 + ... + 1323.

It is an arithmetic number, because the mean of its divisors is an integer number (72144).

2⁶⁴⁴⁹⁶⁶ is an apocalyptic number.

644966 is a deficient number, since it is larger than the sum of its proper divisors (509338).

644966 is a wasteful number, since it uses less digits than its factorization.

644966 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2035.

The product of its digits is 31104, while the sum is 35.

The square root of 644966 is about 803.0977524561. The cubic root of 644966 is about 86.3997077894.

The spelling of 644966 in words is "six hundred forty-four thousand, nine hundred sixty-six".