1291989 has 4 divisors (see below), whose sum is σ = 1722656. Its totient is φ = 861324.

The previous prime is 1291967. The next prime is 1291991. The reversal of 1291989 is 9891921.

It is a happy number.

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 1291989 - 2⁵ = 1291957 is a prime.

It is a super-2 number, since 2×1291989² = 3338471152242, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1291909) 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 3 ways as a sum of consecutive naturals, for example, 215329 + ... + 215334.

It is an arithmetic number, because the mean of its divisors is an integer number (430664).

2^1291989 is an apocalyptic number.

It is an amenable number.

1291989 is a deficient number, since it is larger than the sum of its proper divisors (430667).

1291989 is an equidigital number, since it uses as much as digits as its factorization.

1291989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 430666.

The product of its digits is 11664, while the sum is 39.

The square root of 1291989 is about 1136.6569403298. The cubic root of 1291989 is about 108.9146429357.

Adding to 1291989 its sum of digits (39), we get a triangular number (1292028 = T₁₆₀₇).

The spelling of 1291989 in words is "one million, two hundred ninety-one thousand, nine hundred eighty-nine".