1661321017 has 4 divisors (see below), whose sum is σ = 1670602320. Its totient is φ = 1652039716.

The previous prime is 1661321003. The next prime is 1661321021. The reversal of 1661321017 is 7101231661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7101231661 = 379 ⋅18736759.

It is a cyclic number.

It is not a de Polignac number, because 1661321017 - 2¹⁹ = 1660796729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661351017) 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, 4640383 + ... + 4640740.

It is an arithmetic number, because the mean of its divisors is an integer number (417650580).

Almost surely, 2^1661321017 is an apocalyptic number.

It is an amenable number.

1661321017 is a deficient number, since it is larger than the sum of its proper divisors (9281303).

1661321017 is an equidigital number, since it uses as much as digits as its factorization.

1661321017 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9281302.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 1661321017 is about 40759.3058944826. The cubic root of 1661321017 is about 1184.3621501538.

Adding to 1661321017 its reverse (7101231661), we get a palindrome (8762552678).

The spelling of 1661321017 in words is "one billion, six hundred sixty-one million, three hundred twenty-one thousand, seventeen".