1664869 has 2 divisors, whose sum is σ = 1664870. Its totient is φ = 1664868.

The previous prime is 1664867. The next prime is 1664893. The reversal of 1664869 is 9684661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1292769 + 372100 = 1137^2 + 610^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664869 - 2¹ = 1664867 is a prime.

It is a super-2 number, since 2×1664869² = 5543577574322, which contains 22 as substring.

Together with 1664867, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1664863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832434 + 832435.

It is an arithmetic number, because the mean of its divisors is an integer number (832435).

2^1664869 is an apocalyptic number.

It is an amenable number.

1664869 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664869 is an equidigital number, since it uses as much as digits as its factorization.

1664869 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 40.

The square root of 1664869 is about 1290.2980275890. The cubic root of 1664869 is about 118.5204674243.

The spelling of 1664869 in words is "one million, six hundred sixty-four thousand, eight hundred sixty-nine".