1664817977 has 4 divisors (see below), whose sum is σ = 1668772836. Its totient is φ = 1660863120.

The previous prime is 1664817949. The next prime is 1664817989. The reversal of 1664817977 is 7797184661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7797184661 = 7 ⋅1113883523.

It can be written as a sum of positive squares in 2 ways, for example, as 467381161 + 1197436816 = 21619^2 + 34604^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1664817977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1664817907) 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, 1976798 + ... + 1977639.

It is an arithmetic number, because the mean of its divisors is an integer number (417193209).

Almost surely, 2^1664817977 is an apocalyptic number.

It is an amenable number.

1664817977 is a deficient number, since it is larger than the sum of its proper divisors (3954859).

1664817977 is an equidigital number, since it uses as much as digits as its factorization.

1664817977 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3954858.

The product of its digits is 3556224, while the sum is 56.

The square root of 1664817977 is about 40802.1810323909. The cubic root of 1664817977 is about 1185.1925665205.

The spelling of 1664817977 in words is "one billion, six hundred sixty-four million, eight hundred seventeen thousand, nine hundred seventy-seven".