1991937 has 4 divisors (see below), whose sum is σ = 2655920. Its totient is φ = 1327956.

The previous prime is 1991933. The next prime is 1991947. The reversal of 1991937 is 7391991.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1991937 - 2² = 1991933 is a prime.

It is a D-number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1991895 and 1991904.

It is not an unprimeable number, because it can be changed into a prime (1991933) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 331987 + ... + 331992.

It is an arithmetic number, because the mean of its divisors is an integer number (663980).

2^1991937 is an apocalyptic number.

It is an amenable number.

1991937 is a deficient number, since it is larger than the sum of its proper divisors (663983).

1991937 is an equidigital number, since it uses as much as digits as its factorization.

1991937 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 663982.

The product of its digits is 15309, while the sum is 39.

The square root of 1991937 is about 1411.3599824283. The cubic root of 1991937 is about 125.8225645605.

The spelling of 1991937 in words is "one million, nine hundred ninety-one thousand, nine hundred thirty-seven".