1321220400 has 120 divisors (see below), whose sum is σ = 4249080720. Its totient is φ = 350929920.

The previous prime is 1321220393. The next prime is 1321220401. The reversal of 1321220400 is 40221231.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 1321220400.

It is not an unprimeable number, because it can be changed into a prime (1321220401) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 320754 + ... + 324846.

It is an arithmetic number, because the mean of its divisors is an integer number (35409006).

Almost surely, 2^1321220400 is an apocalyptic number.

1321220400 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 1321220400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2124540360).

1321220400 is an abundant number, since it is smaller than the sum of its proper divisors (2927860320).

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

1321220400 is a wasteful number, since it uses less digits than its factorization.

1321220400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4383 (or 4372 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 1321220400 is about 36348.5955712184. The cubic root of 1321220400 is about 1097.2992698861.

Adding to 1321220400 its reverse (40221231), we get a palindrome (1361441631).

The spelling of 1321220400 in words is "one billion, three hundred twenty-one million, two hundred twenty thousand, four hundred".