1291255640 has 64 divisors (see below), whose sum is σ = 2983145760. Its totient is φ = 502727680.

The previous prime is 1291255619. The next prime is 1291255649. The reversal of 1291255640 is 465521921.

It is a happy number.

It is a super-2 number, since 2×1291255640² = 3334682255663619200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1291255640.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1291255649) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1109699 + ... + 1110861.

Almost surely, 2^1291255640 is an apocalyptic number.

1291255640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1291255640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1491572880).

1291255640 is an abundant number, since it is smaller than the sum of its proper divisors (1691890120).

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

1291255640 is a wasteful number, since it uses less digits than its factorization.

1291255640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1892 (or 1888 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 35.

The square root of 1291255640 is about 35934.0456948560. The cubic root of 1291255640 is about 1088.9403162500.

The spelling of 1291255640 in words is "one billion, two hundred ninety-one million, two hundred fifty-five thousand, six hundred forty".