1961981321 has 2 divisors, whose sum is σ = 1961981322. Its totient is φ = 1961981320.

The previous prime is 1961981317. The next prime is 1961981347. The reversal of 1961981321 is 1231891691.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1348725625 + 613255696 = 36725^2 + 24764^2 .

It is a cyclic number.

It is not a de Polignac number, because 1961981321 - 2² = 1961981317 is a prime.

It is not a weakly prime, because it can be changed into another prime (1961981821) 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 as a sum of consecutive naturals, namely, 980990660 + 980990661.

It is an arithmetic number, because the mean of its divisors is an integer number (980990661).

Almost surely, 2^1961981321 is an apocalyptic number.

It is an amenable number.

1961981321 is a deficient number, since it is larger than the sum of its proper divisors (1).

1961981321 is an equidigital number, since it uses as much as digits as its factorization.

1961981321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 41.

The square root of 1961981321 is about 44294.2583299461. The cubic root of 1961981321 is about 1251.8864999421.

The spelling of 1961981321 in words is "one billion, nine hundred sixty-one million, nine hundred eighty-one thousand, three hundred twenty-one".