1991945061 has 32 divisors (see below), whose sum is σ = 3162597120. Its totient is φ = 1235881152.

The previous prime is 1991945017. The next prime is 1991945077. The reversal of 1991945061 is 1605491991.

1991945061 is a `hidden beast` number, since 199 + 1 + 9 + 450 + 6 + 1 = 666.

It is not a de Polignac number, because 1991945061 - 2¹¹ = 1991943013 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1991944998 and 1991945016.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991943061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 20370 + ... + 66323.

It is an arithmetic number, because the mean of its divisors is an integer number (98831160).

Almost surely, 2^1991945061 is an apocalyptic number.

It is an amenable number.

1991945061 is a deficient number, since it is larger than the sum of its proper divisors (1170652059).

1991945061 is a wasteful number, since it uses less digits than its factorization.

1991945061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86762 (or 86756 counting only the distinct ones).

The product of its (nonzero) digits is 87480, while the sum is 45.

The square root of 1991945061 is about 44631.2117357349. The cubic root of 1991945061 is about 1258.2273428710.

It can be divided in two parts, 19919 and 45061, that added together give a triangular number (64980 = T₃₆₀).

The spelling of 1991945061 in words is "one billion, nine hundred ninety-one million, nine hundred forty-five thousand, sixty-one".