1991679 has 4 divisors (see below), whose sum is σ = 2655576.
Its totient is φ = 1327784.
The previous prime is 1991677. The next prime is 1991681. The reversal of 1991679 is 9761991.
It is a semiprime because it is the product of two primes.
It is an interprime number because it is at equal distance from previous prime (1991677) and next prime (1991681).
It is a cyclic number.
It is not a de Polignac number, because 1991679 - 21 = 1991677 is a prime.
It is a D-number.
It is a zygodrome in base 2.
It is a self number, because there is not a number n which added to its sum of digits gives 1991679.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (1991677) 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, 331944 + ... + 331949.
It is an arithmetic number, because the mean of its divisors is an integer number (663894).
21991679 is an apocalyptic number.
1991679 is a deficient number, since it is larger than the sum of its proper divisors (663897).
1991679 is an equidigital number, since it uses as much as digits as its factorization.
1991679 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 663896.
The product of its digits is 30618, while the sum is 42.
The square root of 1991679 is about 1411.2685782657.
The cubic root of 1991679 is about 125.8171320554.
The spelling of 1991679 in words is "one million, nine hundred ninety-one thousand, six hundred seventy-nine".