1664989 has 4 divisors (see below), whose sum is σ = 1752640. Its totient is φ = 1577340.

The previous prime is 1664987. The next prime is 1665007. The reversal of 1664989 is 9894661.

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: 9894661 = 7 ⋅1413523.

It is a cyclic number.

It is not a de Polignac number, because 1664989 - 2¹ = 1664987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1664987) 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, 43797 + ... + 43834.

It is an arithmetic number, because the mean of its divisors is an integer number (438160).

2^1664989 is an apocalyptic number.

1664989 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

1664989 is a deficient number, since it is larger than the sum of its proper divisors (87651).

1664989 is an equidigital number, since it uses as much as digits as its factorization.

1664989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87650.

The product of its digits is 93312, while the sum is 43.

The square root of 1664989 is about 1290.3445276359. The cubic root of 1664989 is about 118.5233149185.

The spelling of 1664989 in words is "one million, six hundred sixty-four thousand, nine hundred eighty-nine".