1644440140 has 24 divisors (see below), whose sum is σ = 3946656672. Its totient is φ = 563808000.

The previous prime is 1644440113. The next prime is 1644440143. The reversal of 1644440140 is 410444461.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 1644440099 and 1644440108.

It is not an unprimeable number, because it can be changed into a prime (1644440143) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5872861 + ... + 5873140.

It is an arithmetic number, because the mean of its divisors is an integer number (164444028).

Almost surely, 2^1644440140 is an apocalyptic number.

1644440140 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1644440140 is an abundant number, since it is smaller than the sum of its proper divisors (2302216532).

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

1644440140 is a wasteful number, since it uses less digits than its factorization.

1644440140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11746017 (or 11746015 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 28.

The square root of 1644440140 is about 40551.6971284803. The cubic root of 1644440140 is about 1180.3370051506.

The spelling of 1644440140 in words is "one billion, six hundred forty-four million, four hundred forty thousand, one hundred forty".