1664987 has 2 divisors, whose sum is σ = 1664988. Its totient is φ = 1664986.

The previous prime is 1664959. The next prime is 1665007. The reversal of 1664987 is 7894661.

It is a strong prime.

It is an emirp because it is prime and its reverse (7894661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1664987 - 2²⁰ = 616411 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1664287) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832493 + 832494.

It is an arithmetic number, because the mean of its divisors is an integer number (832494).

2^1664987 is an apocalyptic number.

1664987 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664987 is an equidigital number, since it uses as much as digits as its factorization.

1664987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 41.

The square root of 1664987 is about 1290.3437526489. The cubic root of 1664987 is about 118.5232674614.

The spelling of 1664987 in words is "one million, six hundred sixty-four thousand, nine hundred eighty-seven".