12345567781 has 2 divisors, whose sum is σ = 12345567782. Its totient is φ = 12345567780.

The previous prime is 12345567763. The next prime is 12345567797. The reversal of 12345567781 is 18776554321.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6829534881 + 5516032900 = 82641^2 + 74270^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12345567781 is a prime.

It is a super-2 number, since 2×12345567781² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (12345567181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6172783890 + 6172783891.

It is an arithmetic number, because the mean of its divisors is an integer number (6172783891).

Almost surely, 2^12345567781 is an apocalyptic number.

It is an amenable number.

12345567781 is a deficient number, since it is larger than the sum of its proper divisors (1).

12345567781 is an equidigital number, since it uses as much as digits as its factorization.

12345567781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1411200, while the sum is 49.

The spelling of 12345567781 in words is "twelve billion, three hundred forty-five million, five hundred sixty-seven thousand, seven hundred eighty-one".