1644739872 has 96 divisors (see below), whose sum is σ = 4478302080. Its totient is φ = 527923200.

The previous prime is 1644739861. The next prime is 1644739897. The reversal of 1644739872 is 2789374461.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 1672693 + ... + 1673675.

It is an arithmetic number, because the mean of its divisors is an integer number (46648980).

Almost surely, 2^1644739872 is an apocalyptic number.

1644739872 is a gapful number since it is divisible by the number (12) 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 1644739872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2239151040).

1644739872 is an abundant number, since it is smaller than the sum of its proper divisors (2833562208).

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

1644739872 is a wasteful number, since it uses less digits than its factorization.

1644739872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1626 (or 1618 counting only the distinct ones).

The product of its digits is 2032128, while the sum is 51.

The square root of 1644739872 is about 40555.3926377245. The cubic root of 1644739872 is about 1180.4087141110.

It can be divided in two parts, 164473 and 9872, that added together give a triangular number (174345 = T₅₉₀).

The spelling of 1644739872 in words is "one billion, six hundred forty-four million, seven hundred thirty-nine thousand, eight hundred seventy-two".