1291645 has 4 divisors (see below), whose sum is σ = 1549980. Its totient is φ = 1033312.

The previous prime is 1291637. The next prime is 1291669. The reversal of 1291645 is 5461921.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5461921 = 31 ⋅176191.

It can be written as a sum of positive squares in 2 ways, for example, as 669124 + 622521 = 818^2 + 789^2 .

It is a cyclic number.

It is not a de Polignac number, because 1291645 - 2³ = 1291637 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 129160 + ... + 129169.

It is an arithmetic number, because the mean of its divisors is an integer number (387495).

2^1291645 is an apocalyptic number.

It is an amenable number.

1291645 is a deficient number, since it is larger than the sum of its proper divisors (258335).

1291645 is an equidigital number, since it uses as much as digits as its factorization.

1291645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 258334.

The product of its digits is 2160, while the sum is 28.

The square root of 1291645 is about 1136.5056093130. The cubic root of 1291645 is about 108.9049756803.

It can be divided in two parts, 1291 and 645, that multiplied together give a triangular number (832695 = T₁₂₉₀).

The spelling of 1291645 in words is "one million, two hundred ninety-one thousand, six hundred forty-five".