1961991 has 12 divisors (see below), whose sum is σ = 2847832. Its totient is φ = 1301616.

The previous prime is 1961989. The next prime is 1962001. The reversal of 1961991 is 1991691.

It is not a de Polignac number, because 1961991 - 2¹ = 1961989 is a prime.

It is a Duffinian number.

1961991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1960991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2100 + ... + 2886.

2^1961991 is an apocalyptic number.

1961991 is a deficient number, since it is larger than the sum of its proper divisors (885841).

1961991 is a wasteful number, since it uses less digits than its factorization.

1961991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1070 (or 1067 counting only the distinct ones).

The product of its digits is 4374, while the sum is 36.

The square root of 1961991 is about 1400.7108909407. The cubic root of 1961991 is about 125.1888558574.

It can be divided in two parts, 196 and 1991, that added together give a 7-th power (2187 = 3⁷).

The spelling of 1961991 in words is "one million, nine hundred sixty-one thousand, nine hundred ninety-one".