1644136020 has 36 divisors (see below), whose sum is σ = 4987213140. Its totient is φ = 438436224.

The previous prime is 1644136009. The next prime is 1644136027. The reversal of 1644136020 is 206314461.

1644136020 is a `hidden beast` number, since 1 + 6 + 44 + 13 + 602 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1262949444 + 381186576 = 35538^2 + 19524^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-3 number, since 3×1644136020³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644136027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4566865 + ... + 4567224.

Almost surely, 2^1644136020 is an apocalyptic number.

1644136020 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1644136020 is an abundant number, since it is smaller than the sum of its proper divisors (3343077120).

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

1644136020 is a wasteful number, since it uses less digits than its factorization.

1644136020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9134104 (or 9134099 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 1644136020 is about 40547.9471736856. The cubic root of 1644136020 is about 1180.2642374829.

The spelling of 1644136020 in words is "one billion, six hundred forty-four million, one hundred thirty-six thousand, twenty".