644069621 has 32 divisors (see below), whose sum is σ = 746807040. Its totient is φ = 550877184.

The previous prime is 644069617. The next prime is 644069639. The reversal of 644069621 is 126960446.

It is a happy number.

It is not a de Polignac number, because 644069621 - 2² = 644069617 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644069651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1536950 + ... + 1537368.

It is an arithmetic number, because the mean of its divisors is an integer number (23337720).

Almost surely, 2^644069621 is an apocalyptic number.

It is an amenable number.

644069621 is a deficient number, since it is larger than the sum of its proper divisors (102737419).

644069621 is a wasteful number, since it uses less digits than its factorization.

644069621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 605.

The product of its (nonzero) digits is 62208, while the sum is 38.

The square root of 644069621 is about 25378.5267696925. The cubic root of 644069621 is about 863.5966289285.

The spelling of 644069621 in words is "six hundred forty-four million, sixty-nine thousand, six hundred twenty-one".