1321531961 has 4 divisors (see below), whose sum is σ = 1321737252. Its totient is φ = 1321326672.

The previous prime is 1321531951. The next prime is 1321531969. The reversal of 1321531961 is 1691351231.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1691351231 = 2719 ⋅622049.

It can be written as a sum of positive squares in 2 ways, for example, as 379041961 + 942490000 = 19469^2 + 30700^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1321531961 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1321531969) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 92666 + ... + 105971.

It is an arithmetic number, because the mean of its divisors is an integer number (330434313).

Almost surely, 2^1321531961 is an apocalyptic number.

It is an amenable number.

1321531961 is a deficient number, since it is larger than the sum of its proper divisors (205291).

1321531961 is an equidigital number, since it uses as much as digits as its factorization.

1321531961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205290.

The product of its digits is 4860, while the sum is 32.

The square root of 1321531961 is about 36352.8810550141. The cubic root of 1321531961 is about 1097.3855155997.

The spelling of 1321531961 in words is "one billion, three hundred twenty-one million, five hundred thirty-one thousand, nine hundred sixty-one".