1661715641 has 4 divisors (see below), whose sum is σ = 1662423012. Its totient is φ = 1661008272.

The previous prime is 1661715611. The next prime is 1661715697. The reversal of 1661715641 is 1465171661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1465171661 = 167 ⋅8773483.

It can be written as a sum of positive squares in 2 ways, for example, as 408201616 + 1253514025 = 20204^2 + 35405^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661715641 - 2⁶ = 1661715577 is a prime.

It is a super-2 number, since 2×1661715641² = 5522597743088081762, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1661715595 and 1661715604.

It is not an unprimeable number, because it can be changed into a prime (1661715611) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 350150 + ... + 354863.

It is an arithmetic number, because the mean of its divisors is an integer number (415605753).

Almost surely, 2^1661715641 is an apocalyptic number.

It is an amenable number.

1661715641 is a deficient number, since it is larger than the sum of its proper divisors (707371).

1661715641 is an equidigital number, since it uses as much as digits as its factorization.

1661715641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 707370.

The product of its digits is 30240, while the sum is 38.

The square root of 1661715641 is about 40764.1465138178. The cubic root of 1661715641 is about 1184.4559190527.

The spelling of 1661715641 in words is "one billion, six hundred sixty-one million, seven hundred fifteen thousand, six hundred forty-one".