1991407986 has 12 divisors (see below), whose sum is σ = 4314717342. Its totient is φ = 663802656.

The previous prime is 1991407981. The next prime is 1991407987. The reversal of 1991407986 is 6897041991.

It can be written as a sum of positive squares in only one way, i.e., 1143724761 + 847683225 = 33819^2 + 29115^2 .

It is not an unprimeable number, because it can be changed into a prime (1991407981) 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, 55316871 + ... + 55316906.

Almost surely, 2^1991407986 is an apocalyptic number.

1991407986 is an abundant number, since it is smaller than the sum of its proper divisors (2323309356).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1991407986 is a wasteful number, since it uses less digits than its factorization.

1991407986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110633785 (or 110633782 counting only the distinct ones).

The product of its (nonzero) digits is 979776, while the sum is 54.

The square root of 1991407986 is about 44625.1945205844. The cubic root of 1991407986 is about 1258.1142501948.

The spelling of 1991407986 in words is "one billion, nine hundred ninety-one million, four hundred seven thousand, nine hundred eighty-six".