1291240278 has 48 divisors (see below), whose sum is σ = 2910974976. Its totient is φ = 428979240.

The previous prime is 1291240277. The next prime is 1291240289. The reversal of 1291240278 is 8720421921.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1291240271) 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 23 ways as a sum of consecutive naturals, for example, 146875 + ... + 155417.

It is an arithmetic number, because the mean of its divisors is an integer number (60645312).

Almost surely, 2^1291240278 is an apocalyptic number.

1291240278 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1291240278, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1455487488).

1291240278 is an abundant number, since it is smaller than the sum of its proper divisors (1619734698).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1291240278 is an equidigital number, since it uses as much as digits as its factorization.

1291240278 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8871 (or 8859 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The square root of 1291240278 is about 35933.8319415005. The cubic root of 1291240278 is about 1088.9359978778.

The spelling of 1291240278 in words is "one billion, two hundred ninety-one million, two hundred forty thousand, two hundred seventy-eight".