1287166661 has 6 divisors (see below), whose sum is σ = 1414819686. Its totient is φ = 1170151400.

The previous prime is 1287166631. The next prime is 1287166667. The reversal of 1287166661 is 1666617821.

It can be written as a sum of positive squares in only one way, i.e., 676780225 + 610386436 = 26015^2 + 24706^2 .

It is not a de Polignac number, because 1287166661 - 2¹⁰ = 1287165637 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 (1287166667) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5318750 + ... + 5318991.

It is an arithmetic number, because the mean of its divisors is an integer number (235803281).

Almost surely, 2^1287166661 is an apocalyptic number.

1287166661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1287166661 is a deficient number, since it is larger than the sum of its proper divisors (127653025).

1287166661 is a wasteful number, since it uses less digits than its factorization.

1287166661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10637763 (or 10637752 counting only the distinct ones).

The product of its digits is 145152, while the sum is 44.

The square root of 1287166661 is about 35877.1049696042. The cubic root of 1287166661 is about 1087.7896630253.

The spelling of 1287166661 in words is "one billion, two hundred eighty-seven million, one hundred sixty-six thousand, six hundred sixty-one".