1643725440 has 512 divisors, whose sum is σ = 6768230400. Its totient is φ = 369266688.

The previous prime is 1643725403. The next prime is 1643725477. The reversal of 1643725440 is 445273461.

1643725440 is a `hidden beast` number, since 1 + 6 + 43 + 72 + 544 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (1643725403) and next prime (1643725477).

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 = 1643725395 and 1643725404.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 12942657 + ... + 12942783.

It is an arithmetic number, because the mean of its divisors is an integer number (13219200).

Almost surely, 2^1643725440 is an apocalyptic number.

1643725440 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 1643725440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3384115200).

1643725440 is an abundant number, since it is smaller than the sum of its proper divisors (5124504960).

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

1643725440 is a wasteful number, since it uses less digits than its factorization.

1643725440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269 (or 251 counting only the distinct ones).

The product of its (nonzero) digits is 80640, while the sum is 36.

The square root of 1643725440 is about 40542.8839625402. The cubic root of 1643725440 is about 1180.1659825883.

The spelling of 1643725440 in words is "one billion, six hundred forty-three million, seven hundred twenty-five thousand, four hundred forty".