12129781 has 2 divisors, whose sum is σ = 12129782. Its totient is φ = 12129780.

The previous prime is 12129769. The next prime is 12129811. The reversal of 12129781 is 18792121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6682225 + 5447556 = 2585^2 + 2334^2 .

It is a cyclic number.

It is not a de Polignac number, because 12129781 - 2¹¹ = 12127733 is a prime.

It is a super-2 number, since 2×12129781² = 294263174215922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (12129701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6064890 + 6064891.

It is an arithmetic number, because the mean of its divisors is an integer number (6064891).

Almost surely, 2^12129781 is an apocalyptic number.

It is an amenable number.

12129781 is a deficient number, since it is larger than the sum of its proper divisors (1).

12129781 is an equidigital number, since it uses as much as digits as its factorization.

12129781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2016, while the sum is 31.

The square root of 12129781 is about 3482.7835132262. The cubic root of 12129781 is about 229.7652361956.

It can be divided in two parts, 12129 and 781, that multiplied together give a palindrome (9472749).

The spelling of 12129781 in words is "twelve million, one hundred twenty-nine thousand, seven hundred eighty-one".