1643653440 has 504 divisors, whose sum is σ = 6700101408. Its totient is φ = 366612480.

The previous prime is 1643653421. The next prime is 1643653471. The reversal of 1643653440 is 443563461.

1643653440 is a `hidden beast` number, since 1 + 643 + 6 + 5 + 3 + 4 + 4 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 1643653395 and 1643653404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 5353767 + ... + 5354073.

It is an arithmetic number, because the mean of its divisors is an integer number (13293852).

Almost surely, 2^1643653440 is an apocalyptic number.

1643653440 is a gapful number since it is divisible by the number (10) 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 1643653440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3350050704).

1643653440 is an abundant number, since it is smaller than the sum of its proper divisors (5056447968).

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

1643653440 is a wasteful number, since it uses less digits than its factorization.

1643653440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 367 (or 341 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 36.

The square root of 1643653440 is about 40541.9960041437. The cubic root of 1643653440 is about 1180.1487507584.

The spelling of 1643653440 in words is "one billion, six hundred forty-three million, six hundred fifty-three thousand, four hundred forty".