644047381 has 8 divisors (see below), whose sum is σ = 655099200. Its totient is φ = 633074112.

The previous prime is 644047379. The next prime is 644047387. The reversal of 644047381 is 183740446.

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

It is a cyclic number.

It is not a de Polignac number, because 644047381 - 2¹ = 644047379 is a prime.

It is a super-2 number, since 2×644047381² = 829594057945918322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644047381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644047387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2980 + ... + 36013.

It is an arithmetic number, because the mean of its divisors is an integer number (81887400).

Almost surely, 2^644047381 is an apocalyptic number.

It is an amenable number.

644047381 is a deficient number, since it is larger than the sum of its proper divisors (11051819).

644047381 is a wasteful number, since it uses less digits than its factorization.

644047381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39275.

The product of its (nonzero) digits is 64512, while the sum is 37.

The square root of 644047381 is about 25378.0886002079. The cubic root of 644047381 is about 863.5866886936.

The spelling of 644047381 in words is "six hundred forty-four million, forty-seven thousand, three hundred eighty-one".