1243055991 has 8 divisors (see below), whose sum is σ = 1661736960. Its totient is φ = 826539512.

The previous prime is 1243055941. The next prime is 1243056043. The reversal of 1243055991 is 1995503421.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1243055991 - 2¹¹ = 1243053943 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1243055921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 539781 + ... + 542078.

It is an arithmetic number, because the mean of its divisors is an integer number (207717120).

Almost surely, 2^1243055991 is an apocalyptic number.

1243055991 is a deficient number, since it is larger than the sum of its proper divisors (418680969).

1243055991 is a wasteful number, since it uses less digits than its factorization.

1243055991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1082245.

The product of its (nonzero) digits is 48600, while the sum is 39.

The square root of 1243055991 is about 35256.9991774683. Note that the first 3 decimals coincide. The cubic root of 1243055991 is about 1075.2189180259.

The spelling of 1243055991 in words is "one billion, two hundred forty-three million, fifty-five thousand, nine hundred ninety-one".