1321165440 has 576 divisors, whose sum is σ = 5514462720. Its totient is φ = 290304000.

The previous prime is 1321165403. The next prime is 1321165453. The reversal of 1321165440 is 445611231.

It is a happy number.

1321165440 is a `hidden beast` number, since 1 + 3 + 2 + 1 + 1 + 654 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (576).

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, 8749365 + ... + 8749515.

It is an arithmetic number, because the mean of its divisors is an integer number (9573720).

Almost surely, 2^1321165440 is an apocalyptic number.

1321165440 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 1321165440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2757231360).

1321165440 is an abundant number, since it is smaller than the sum of its proper divisors (4193297280).

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

1321165440 is a wasteful number, since it uses less digits than its factorization.

1321165440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221 (or 199 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 1321165440 is about 36347.8395506528. The cubic root of 1321165440 is about 1097.2840545584.

Adding to 1321165440 its reverse (445611231), we get a palindrome (1766776671).

The spelling of 1321165440 in words is "one billion, three hundred twenty-one million, one hundred sixty-five thousand, four hundred forty".