1305991 has 6 divisors (see below), whose sum is σ = 1387640. Its totient is φ = 1228896.

The previous prime is 1305971. The next prime is 1306001. The reversal of 1305991 is 1995031.

It is not a de Polignac number, because 1305991 - 2⁵ = 1305959 is a prime.

It is a super-2 number, since 2×1305991² = 3411224984162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1305961) 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 5 ways as a sum of consecutive naturals, for example, 1971 + ... + 2548.

2^1305991 is an apocalyptic number.

1305991 is a deficient number, since it is larger than the sum of its proper divisors (81649).

1305991 is an equidigital number, since it uses as much as digits as its factorization.

1305991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4553 (or 4536 counting only the distinct ones).

The product of its (nonzero) digits is 1215, while the sum is 28.

The square root of 1305991 is about 1142.7996324816. The cubic root of 1305991 is about 109.3066861575.

The spelling of 1305991 in words is "one million, three hundred five thousand, nine hundred ninety-one".