1287661 has 2 divisors, whose sum is σ = 1287662. Its totient is φ = 1287660.

The previous prime is 1287623. The next prime is 1287683. The reversal of 1287661 is 1667821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1012036 + 275625 = 1006^2 + 525^2 .

It is an emirp because it is prime and its reverse (1667821) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1287661 is a prime.

It is equal to p₉₉₁₅₇ and since 1287661 and 99157 have the same sum of digits, it is a Honaker prime.

It is a nialpdrome in base 6.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1287691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 643830 + 643831.

It is an arithmetic number, because the mean of its divisors is an integer number (643831).

2^1287661 is an apocalyptic number.

It is an amenable number.

1287661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1287661 is an equidigital number, since it uses as much as digits as its factorization.

1287661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 31.

The square root of 1287661 is about 1134.7515146498. The cubic root of 1287661 is about 108.7928901153.

The spelling of 1287661 in words is "one million, two hundred eighty-seven thousand, six hundred sixty-one".