1644440400 has 240 divisors, whose sum is σ = 5990797120. Its totient is φ = 428198400.

The previous prime is 1644440387. The next prime is 1644440401. The reversal of 1644440400 is 40444461.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644440401) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 462630 + ... + 466170.

Almost surely, 2^1644440400 is an apocalyptic number.

1644440400 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1644440400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2995398560).

1644440400 is an abundant number, since it is smaller than the sum of its proper divisors (4346356720).

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

1644440400 is a wasteful number, since it uses less digits than its factorization.

1644440400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3611 (or 3594 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 27.

The square root of 1644440400 is about 40551.7003342647. The cubic root of 1644440400 is about 1180.3370673577.

Adding to 1644440400 its reverse (40444461), we get a palindrome (1684884861).

The spelling of 1644440400 in words is "one billion, six hundred forty-four million, four hundred forty thousand, four hundred".