1644405136 has 80 divisors (see below), whose sum is σ = 3565218240. Its totient is φ = 728399360.

The previous prime is 1644405127. The next prime is 1644405149. The reversal of 1644405136 is 6315044461.

It is a super-3 number, since 3×1644405136³ (a number of 29 digits) contains 333 as substring.

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1613235 + ... + 1614253.

It is an arithmetic number, because the mean of its divisors is an integer number (44565228).

Almost surely, 2^1644405136 is an apocalyptic number.

1644405136 is a gapful number since it is divisible by the number (16) 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 1644405136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1782609120).

1644405136 is an abundant number, since it is smaller than the sum of its proper divisors (1920813104).

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

1644405136 is a wasteful number, since it uses less digits than its factorization.

1644405136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1264 (or 1258 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 34.

The square root of 1644405136 is about 40551.2655289573. The cubic root of 1644405136 is about 1180.3286300997.

Adding to 1644405136 its reverse (6315044461), we get a palindrome (7959449597).

The spelling of 1644405136 in words is "one billion, six hundred forty-four million, four hundred five thousand, one hundred thirty-six".