1291400820 has 60 divisors (see below), whose sum is σ = 4051177284. Its totient is φ = 344373120.

The previous prime is 1291400743. The next prime is 1291400837. The reversal of 1291400820 is 280041921.

It can be written as a sum of positive squares in 2 ways, for example, as 348419556 + 942981264 = 18666^2 + 30708^2 .

It is a tau number, because it is divible by the number of its divisors (60).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

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 19 ways as a sum of consecutive naturals, for example, 396961 + ... + 400200.

Almost surely, 2^1291400820 is an apocalyptic number.

1291400820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1291400820 is an abundant number, since it is smaller than the sum of its proper divisors (2759776464).

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

1291400820 is a wasteful number, since it uses less digits than its factorization.

1291400820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 797182 (or 797171 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 1291400820 is about 35936.0657279007. The cubic root of 1291400820 is about 1088.9811257344.

The spelling of 1291400820 in words is "one billion, two hundred ninety-one million, four hundred thousand, eight hundred twenty".