644492906 has 8 divisors (see below), whose sum is σ = 968086080. Its totient is φ = 321797548.

The previous prime is 644492887. The next prime is 644492917. The reversal of 644492906 is 609294446.

644492906 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a super-2 number, since 2×644492906² = 830742211768649672, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 222656 + ... + 225531.

It is an arithmetic number, because the mean of its divisors is an integer number (121010760).

Almost surely, 2^644492906 is an apocalyptic number.

644492906 is a deficient number, since it is larger than the sum of its proper divisors (323593174).

644492906 is a wasteful number, since it uses less digits than its factorization.

644492906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 448908.

The product of its (nonzero) digits is 373248, while the sum is 44.

The square root of 644492906 is about 25386.8648320347. The cubic root of 644492906 is about 863.7857738267.

The spelling of 644492906 in words is "six hundred forty-four million, four hundred ninety-two thousand, nine hundred six".