1720661161 has 4 divisors (see below), whose sum is σ = 1722534400. Its totient is φ = 1718787924.

The previous prime is 1720661153. The next prime is 1720661167. The reversal of 1720661161 is 1611660271.

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.

It is a cyclic number.

It is not a de Polignac number, because 1720661161 - 2³ = 1720661153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1720661167) 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, 935241 + ... + 937078.

It is an arithmetic number, because the mean of its divisors is an integer number (430633600).

Almost surely, 2^1720661161 is an apocalyptic number.

It is an amenable number.

1720661161 is a deficient number, since it is larger than the sum of its proper divisors (1873239).

1720661161 is an equidigital number, since it uses as much as digits as its factorization.

1720661161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1873238.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 1720661161 is about 41480.8529444610. The cubic root of 1720661161 is about 1198.2987840358.

The spelling of 1720661161 in words is "one billion, seven hundred twenty million, six hundred sixty-one thousand, one hundred sixty-one".