1321728440 has 16 divisors (see below), whose sum is σ = 2973889080. Its totient is φ = 528691360.

The previous prime is 1321728433. The next prime is 1321728449. The reversal of 1321728440 is 448271231.

It is a junction number, because it is equal to n+sod(n) for n = 1321728397 and 1321728406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1321728449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16521566 + ... + 16521645.

Almost surely, 2^1321728440 is an apocalyptic number.

1321728440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1321728440 is an abundant number, since it is smaller than the sum of its proper divisors (1652160640).

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

1321728440 is a wasteful number, since it uses less digits than its factorization.

1321728440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33043222 (or 33043218 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 32.

The square root of 1321728440 is about 36355.5833401143. The cubic root of 1321728440 is about 1097.4398975671.

Adding to 1321728440 its reverse (448271231), we get a palindrome (1769999671).

The spelling of 1321728440 in words is "one billion, three hundred twenty-one million, seven hundred twenty-eight thousand, four hundred forty".