1661171887 has 2 divisors, whose sum is σ = 1661171888. Its totient is φ = 1661171886.

The previous prime is 1661171873. The next prime is 1661171893. The reversal of 1661171887 is 7881711661.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (7881711661) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1661171887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661171287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830585943 + 830585944.

It is an arithmetic number, because the mean of its divisors is an integer number (830585944).

Almost surely, 2^1661171887 is an apocalyptic number.

1661171887 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661171887 is an equidigital number, since it uses as much as digits as its factorization.

1661171887 is an evil number, because the sum of its binary digits is even.

The product of its digits is 112896, while the sum is 46.

The square root of 1661171887 is about 40757.4764552468. The cubic root of 1661171887 is about 1184.3267106429.

The spelling of 1661171887 in words is "one billion, six hundred sixty-one million, one hundred seventy-one thousand, eight hundred eighty-seven".