1644991368 has 16 divisors (see below), whose sum is σ = 4112478480. Its totient is φ = 548330448.

The previous prime is 1644991363. The next prime is 1644991391. The reversal of 1644991368 is 8631994461.

It is a super-2 number, since 2×1644991368² = 5411993201589022848, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1644991368.

It is not an unprimeable number, because it can be changed into a prime (1644991363) 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 3 ways as a sum of consecutive naturals, for example, 34270630 + ... + 34270677.

It is an arithmetic number, because the mean of its divisors is an integer number (257029905).

Almost surely, 2^1644991368 is an apocalyptic number.

It is an amenable number.

1644991368 is an abundant number, since it is smaller than the sum of its proper divisors (2467487112).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1644991368 is a wasteful number, since it uses less digits than its factorization.

1644991368 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68541316 (or 68541312 counting only the distinct ones).

The product of its digits is 1119744, while the sum is 51.

The square root of 1644991368 is about 40558.4931672763. The cubic root of 1644991368 is about 1180.4688761960.

The spelling of 1644991368 in words is "one billion, six hundred forty-four million, nine hundred ninety-one thousand, three hundred sixty-eight".