1323721728 has 396 divisors, whose sum is σ = 4705676352. Its totient is φ = 350945280.

The previous prime is 1323721723. The next prime is 1323721739. The reversal of 1323721728 is 8271273231.

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

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 1323721692 and 1323721701.

It is not an unprimeable number, because it can be changed into a prime (1323721723) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 18643933 + ... + 18644003.

Almost surely, 2^1323721728 is an apocalyptic number.

1323721728 is a gapful number since it is divisible by the number (18) 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 1323721728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2352838176).

1323721728 is an abundant number, since it is smaller than the sum of its proper divisors (3381954624).

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

1323721728 is a wasteful number, since it uses less digits than its factorization.

1323721728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138 (or 100 counting only the distinct ones).

The product of its digits is 28224, while the sum is 36.

The square root of 1323721728 is about 36382.9867932802. The cubic root of 1323721728 is about 1097.9913005572.

Adding to 1323721728 its reverse (8271273231), we get a palindrome (9594994959).

The spelling of 1323721728 in words is "one billion, three hundred twenty-three million, seven hundred twenty-one thousand, seven hundred twenty-eight".