1664881 has 4 divisors (see below), whose sum is σ = 1700352. Its totient is φ = 1629412.

The previous prime is 1664869. The next prime is 1664893. The reversal of 1664881 is 1884661.

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: 1884661 = 1231 ⋅1531.

It is an interprime number because it is at equal distance from previous prime (1664869) and next prime (1664893).

It is a cyclic number.

It is not a de Polignac number, because 1664881 - 2⁵ = 1664849 is a prime.

It is a super-2 number, since 2×1664881² = 5543657488322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1664801) 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, 17665 + ... + 17758.

It is an arithmetic number, because the mean of its divisors is an integer number (425088).

2^1664881 is an apocalyptic number.

It is an amenable number.

1664881 is a deficient number, since it is larger than the sum of its proper divisors (35471).

1664881 is an equidigital number, since it uses as much as digits as its factorization.

1664881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35470.

The product of its digits is 9216, while the sum is 34.

The square root of 1664881 is about 1290.3026776691. The cubic root of 1664881 is about 118.5207521799.

The spelling of 1664881 in words is "one million, six hundred sixty-four thousand, eight hundred eighty-one".