1644642381 has 8 divisors (see below), whose sum is σ = 2193057280. Its totient is φ = 1096327872.

The previous prime is 1644642317. The next prime is 1644642397. The reversal of 1644642381 is 1832464461.

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

It is not a de Polignac number, because 1644642381 - 2⁶ = 1644642317 is a prime.

It is a super-2 number, since 2×1644642381² = 5409697122762698322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644642281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31125 + ... + 65253.

It is an arithmetic number, because the mean of its divisors is an integer number (274132160).

Almost surely, 2^1644642381 is an apocalyptic number.

It is an amenable number.

1644642381 is a deficient number, since it is larger than the sum of its proper divisors (548414899).

1644642381 is a wasteful number, since it uses less digits than its factorization.

1644642381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50195.

The product of its digits is 110592, while the sum is 39.

The square root of 1644642381 is about 40554.1906712488. The cubic root of 1644642381 is about 1180.3853909700.

The spelling of 1644642381 in words is "one billion, six hundred forty-four million, six hundred forty-two thousand, three hundred eighty-one".