1285991 has 4 divisors (see below), whose sum is σ = 1469712. Its totient is φ = 1102272.

The previous prime is 1285981. The next prime is 1285993. The reversal of 1285991 is 1995821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1995821 = 53 ⋅37657.

It is a cyclic number.

It is not a de Polignac number, because 1285991 - 2¹⁰ = 1284967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1285993) 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, 91850 + ... + 91863.

It is an arithmetic number, because the mean of its divisors is an integer number (367428).

2^1285991 is an apocalyptic number.

1285991 is a deficient number, since it is larger than the sum of its proper divisors (183721).

1285991 is an equidigital number, since it uses as much as digits as its factorization.

1285991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 183720.

The product of its digits is 6480, while the sum is 35.

The square root of 1285991 is about 1134.0154319938. The cubic root of 1285991 is about 108.7458376881.

Subtracting from 1285991 its sum of digits (35), we obtain a square (1285956 = 1134²).

The spelling of 1285991 in words is "one million, two hundred eighty-five thousand, nine hundred ninety-one".