1231780865 has 12 divisors (see below), whose sum is σ = 1719465876. Its totient is φ = 844649568.

The previous prime is 1231780831. The next prime is 1231780867. The reversal of 1231780865 is 5680871321.

It can be written as a sum of positive squares in 2 ways, for example, as 707187649 + 524593216 = 26593^2 + 22904^2 .

It is not a de Polignac number, because 1231780865 - 2¹⁴ = 1231764481 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1231780867) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2513594 + ... + 2514083.

It is an arithmetic number, because the mean of its divisors is an integer number (143288823).

Almost surely, 2^1231780865 is an apocalyptic number.

It is an amenable number.

1231780865 is a deficient number, since it is larger than the sum of its proper divisors (487685011).

1231780865 is an equidigital number, since it uses as much as digits as its factorization.

1231780865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5027696 (or 5027689 counting only the distinct ones).

The product of its (nonzero) digits is 80640, while the sum is 41.

The square root of 1231780865 is about 35096.7358168819. The cubic root of 1231780865 is about 1071.9581185024.

The spelling of 1231780865 in words is "one billion, two hundred thirty-one million, seven hundred eighty thousand, eight hundred sixty-five".