1664316681 has 4 divisors (see below), whose sum is σ = 2219088912. Its totient is φ = 1109544452.

The previous prime is 1664316631. The next prime is 1664316701. The reversal of 1664316681 is 1866134661.

It is a happy number.

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: 1866134661 = 3 ⋅622044887.

It is a cyclic number.

It is not a de Polignac number, because 1664316681 - 2²² = 1660122377 is a prime.

It is a super-2 number, since 2×1664316681² = 5539900029309711522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1664316601) 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, 277386111 + ... + 277386116.

It is an arithmetic number, because the mean of its divisors is an integer number (554772228).

Almost surely, 2^1664316681 is an apocalyptic number.

It is an amenable number.

1664316681 is a deficient number, since it is larger than the sum of its proper divisors (554772231).

1664316681 is an equidigital number, since it uses as much as digits as its factorization.

1664316681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 554772230.

The product of its digits is 124416, while the sum is 42.

The square root of 1664316681 is about 40796.0375649401. The cubic root of 1664316681 is about 1185.0735961697.

The spelling of 1664316681 in words is "one billion, six hundred sixty-four million, three hundred sixteen thousand, six hundred eighty-one".