1639987 has 2 divisors, whose sum is σ = 1639988. Its totient is φ = 1639986.

The previous prime is 1639949. The next prime is 1639991. The reversal of 1639987 is 7899361.

It is a strong prime.

It is an emirp because it is prime and its reverse (7899361) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1639987 is a prime.

It is not a weakly prime, because it can be changed into another prime (1639907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 819993 + 819994.

It is an arithmetic number, because the mean of its divisors is an integer number (819994).

2^1639987 is an apocalyptic number.

1639987 is a deficient number, since it is larger than the sum of its proper divisors (1).

1639987 is an equidigital number, since it uses as much as digits as its factorization.

1639987 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 81648, while the sum is 43.

The square root of 1639987 is about 1280.6197718292. The cubic root of 1639987 is about 117.9270592019.

The spelling of 1639987 in words is "one million, six hundred thirty-nine thousand, nine hundred eighty-seven".