1321557120 has 640 divisors, whose sum is σ = 5318414640. Its totient is φ = 310542336.

The previous prime is 1321557113. The next prime is 1321557121. The reversal of 1321557120 is 217551231.

It can be written as a sum of positive squares in 8 ways, for example, as 760435776 + 561121344 = 27576^2 + 23688^2 .

It is a tau number, because it is divible by the number of its divisors (640).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (1321557121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 24935014 + ... + 24935066.

Almost surely, 2^1321557120 is an apocalyptic number.

1321557120 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 1321557120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2659207320).

1321557120 is an abundant number, since it is smaller than the sum of its proper divisors (3996857520).

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

1321557120 is a wasteful number, since it uses less digits than its factorization.

1321557120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134 (or 113 counting only the distinct ones).

The product of its (nonzero) digits is 2100, while the sum is 27.

The square root of 1321557120 is about 36353.2270919653. The cubic root of 1321557120 is about 1097.3924794739.

The spelling of 1321557120 in words is "one billion, three hundred twenty-one million, five hundred fifty-seven thousand, one hundred twenty".