1287989 has 2 divisors, whose sum is σ = 1287990. Its totient is φ = 1287988.

The previous prime is 1287983. The next prime is 1287997. The reversal of 1287989 is 9897821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1067089 + 220900 = 1033^2 + 470^2 .

It is a cyclic number.

It is not a de Polignac number, because 1287989 - 2⁴ = 1287973 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1287983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 643994 + 643995.

It is an arithmetic number, because the mean of its divisors is an integer number (643995).

2^1287989 is an apocalyptic number.

It is an amenable number.

1287989 is a deficient number, since it is larger than the sum of its proper divisors (1).

1287989 is an equidigital number, since it uses as much as digits as its factorization.

1287989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 44.

The square root of 1287989 is about 1134.8960304803. The cubic root of 1287989 is about 108.8021267696.

The spelling of 1287989 in words is "one million, two hundred eighty-seven thousand, nine hundred eighty-nine".