1963991 has 4 divisors (see below), whose sum is σ = 1966800. Its totient is φ = 1961184.

The previous prime is 1963981. The next prime is 1963999. The reversal of 1963991 is 1993691.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1993691 = 7 ⋅284813.

It is a cyclic number.

It is not a de Polignac number, because 1963991 - 2¹⁰ = 1962967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1963999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 575 + ... + 2063.

It is an arithmetic number, because the mean of its divisors is an integer number (491700).

2^1963991 is an apocalyptic number.

1963991 is a deficient number, since it is larger than the sum of its proper divisors (2809).

1963991 is a wasteful number, since it uses less digits than its factorization.

1963991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2808.

The product of its digits is 13122, while the sum is 38.

The square root of 1963991 is about 1401.4246322939. The cubic root of 1963991 is about 125.2313794442.

The spelling of 1963991 in words is "one million, nine hundred sixty-three thousand, nine hundred ninety-one".