1291643388 has 48 divisors (see below), whose sum is σ = 3827093760. Its totient is φ = 369040752.

The previous prime is 1291643369. The next prime is 1291643411. The reversal of 1291643388 is 8833461921.

1291643388 is a `hidden beast` number, since 129 + 16 + 433 + 88 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 853506 + ... + 855017.

It is an arithmetic number, because the mean of its divisors is an integer number (79731120).

Almost surely, 2^1291643388 is an apocalyptic number.

1291643388 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

1291643388 is an abundant number, since it is smaller than the sum of its proper divisors (2535450372).

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

1291643388 is a wasteful number, since it uses less digits than its factorization.

1291643388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1708543 (or 1708535 counting only the distinct ones).

The product of its digits is 248832, while the sum is 45.

The square root of 1291643388 is about 35939.4405632586. The cubic root of 1291643388 is about 1089.0493037502.

The spelling of 1291643388 in words is "one billion, two hundred ninety-one million, six hundred forty-three thousand, three hundred eighty-eight".