1669681 has 4 divisors (see below), whose sum is σ = 1798132. Its totient is φ = 1541232.

The previous prime is 1669651. The next prime is 1669687. The reversal of 1669681 is 1869661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1869661 = 421 ⋅4441.

It can be written as a sum of positive squares in 2 ways, for example, as 129600 + 1540081 = 360^2 + 1241^2 .

It is a cyclic number.

It is not a de Polignac number, because 1669681 - 2⁵ = 1669649 is a prime.

It is a super-2 number, since 2×1669681² = 5575669283522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1669681.

It is not an unprimeable number, because it can be changed into a prime (1669687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64206 + ... + 64231.

It is an arithmetic number, because the mean of its divisors is an integer number (449533).

2^1669681 is an apocalyptic number.

It is an amenable number.

1669681 is a deficient number, since it is larger than the sum of its proper divisors (128451).

1669681 is a wasteful number, since it uses less digits than its factorization.

1669681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128450.

The product of its digits is 15552, while the sum is 37.

The square root of 1669681 is about 1292.1613676318. The cubic root of 1669681 is about 118.6345448484.

The spelling of 1669681 in words is "one million, six hundred sixty-nine thousand, six hundred eighty-one".