1979991 has 16 divisors (see below), whose sum is σ = 3159520. Its totient is φ = 1218240.

The previous prime is 1979947. The next prime is 1979993. The reversal of 1979991 is 1999791.

It is not a de Polignac number, because 1979991 - 2¹³ = 1971799 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1979993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2470 + ... + 3171.

It is an arithmetic number, because the mean of its divisors is an integer number (197470).

2^1979991 is an apocalyptic number.

1979991 is a deficient number, since it is larger than the sum of its proper divisors (1179529).

1979991 is a wasteful number, since it uses less digits than its factorization.

1979991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5663 (or 5657 counting only the distinct ones).

The product of its digits is 45927, while the sum is 45.

The square root of 1979991 is about 1407.1215299326. The cubic root of 1979991 is about 125.5705333054.

The spelling of 1979991 in words is "one million, nine hundred seventy-nine thousand, nine hundred ninety-one".