644355381 has 8 divisors (see below), whose sum is σ = 859364640. Its totient is φ = 429458192.

The previous prime is 644355323. The next prime is 644355421. The reversal of 644355381 is 183553446.

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 644355381 - 2⁹ = 644354869 is a prime.

It is a super-2 number, since 2×644355381² = 830387714047310322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644355781) 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, 13530 + ... + 38363.

It is an arithmetic number, because the mean of its divisors is an integer number (107420580).

Almost surely, 2^644355381 is an apocalyptic number.

It is an amenable number.

644355381 is a deficient number, since it is larger than the sum of its proper divisors (215009259).

644355381 is a wasteful number, since it uses less digits than its factorization.

644355381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56035.

The product of its digits is 172800, while the sum is 39.

The square root of 644355381 is about 25384.1561017892. The cubic root of 644355381 is about 863.7243298667.

The spelling of 644355381 in words is "six hundred forty-four million, three hundred fifty-five thousand, three hundred eighty-one".