1291681 has 4 divisors (see below), whose sum is σ = 1300500. Its totient is φ = 1282864.

The previous prime is 1291673. The next prime is 1291691. The reversal of 1291681 is 1861921.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 341056 + 950625 = 584^2 + 975^2 .

It is a cyclic number.

It is not a de Polignac number, because 1291681 - 2³ = 1291673 is a prime.

It is a super-2 number, since 2×1291681² = 3336879611522, which contains 22 as substring.

It is a Duffinian number.

1291681 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1291691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4186 + ... + 4483.

It is an arithmetic number, because the mean of its divisors is an integer number (325125).

2^1291681 is an apocalyptic number.

It is an amenable number.

1291681 is a deficient number, since it is larger than the sum of its proper divisors (8819).

1291681 is an equidigital number, since it uses as much as digits as its factorization.

1291681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8818.

The product of its digits is 864, while the sum is 28.

The square root of 1291681 is about 1136.5214472239. The cubic root of 1291681 is about 108.9059874502.

The spelling of 1291681 in words is "one million, two hundred ninety-one thousand, six hundred eighty-one".