1644645776 has 40 divisors (see below), whose sum is σ = 3378429600. Its totient is φ = 773418240.

The previous prime is 1644645763. The next prime is 1644645787. The reversal of 1644645776 is 6775464461.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22796 + ... + 61716.

It is an arithmetic number, because the mean of its divisors is an integer number (84460740).

Almost surely, 2^1644645776 is an apocalyptic number.

1644645776 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 1644645776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1689214800).

1644645776 is an abundant number, since it is smaller than the sum of its proper divisors (1733783824).

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

1644645776 is a wasteful number, since it uses less digits than its factorization.

1644645776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39087 (or 39081 counting only the distinct ones).

The product of its digits is 3386880, while the sum is 50.

The square root of 1644645776 is about 40554.2325288002. The cubic root of 1644645776 is about 1180.3862031842.

The spelling of 1644645776 in words is "one billion, six hundred forty-four million, six hundred forty-five thousand, seven hundred seventy-six".