1986661891 has 2 divisors, whose sum is σ = 1986661892. Its totient is φ = 1986661890.

The previous prime is 1986661883. The next prime is 1986661903. The reversal of 1986661891 is 1981666891.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1986661891 - 2³ = 1986661883 is a prime.

It is not a weakly prime, because it can be changed into another prime (1986661591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 993330945 + 993330946.

It is an arithmetic number, because the mean of its divisors is an integer number (993330946).

Almost surely, 2^1986661891 is an apocalyptic number.

1986661891 is a deficient number, since it is larger than the sum of its proper divisors (1).

1986661891 is an equidigital number, since it uses as much as digits as its factorization.

1986661891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1119744, while the sum is 55.

The square root of 1986661891 is about 44571.9854953759. The cubic root of 1986661891 is about 1257.1139730506.

The spelling of 1986661891 in words is "one billion, nine hundred eighty-six million, six hundred sixty-one thousand, eight hundred ninety-one".