1645671664 has 120 divisors (see below), whose sum is σ = 4061385888. Its totient is φ = 640120320.

The previous prime is 1645671661. The next prime is 1645671691. The reversal of 1645671664 is 4661765461.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1645671661) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 620389 + ... + 623035.

Almost surely, 2^1645671664 is an apocalyptic number.

1645671664 is a gapful number since it is divisible by the number (14) 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 1645671664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2030692944).

1645671664 is an abundant number, since it is smaller than the sum of its proper divisors (2415714224).

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

1645671664 is a wasteful number, since it uses less digits than its factorization.

1645671664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2743 (or 2730 counting only the distinct ones).

The product of its digits is 725760, while the sum is 46.

The square root of 1645671664 is about 40566.8789038546. The cubic root of 1645671664 is about 1180.6315837520.

The spelling of 1645671664 in words is "one billion, six hundred forty-five million, six hundred seventy-one thousand, six hundred sixty-four".