1661263321 has 2 divisors, whose sum is σ = 1661263322. Its totient is φ = 1661263320.

The previous prime is 1661263313. The next prime is 1661263337. The reversal of 1661263321 is 1233621661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1183360000 + 477903321 = 34400^2 + 21861^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661263321 - 2³ = 1661263313 is a prime.

It is not a weakly prime, because it can be changed into another prime (1661263381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830631660 + 830631661.

It is an arithmetic number, because the mean of its divisors is an integer number (830631661).

Almost surely, 2^1661263321 is an apocalyptic number.

It is an amenable number.

1661263321 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661263321 is an equidigital number, since it uses as much as digits as its factorization.

1661263321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7776, while the sum is 31.

The square root of 1661263321 is about 40758.5981235861. The cubic root of 1661263321 is about 1184.3484394282.

Adding to 1661263321 its reverse (1233621661), we get a palindrome (2894884982).

The spelling of 1661263321 in words is "one billion, six hundred sixty-one million, two hundred sixty-three thousand, three hundred twenty-one".