1256842129 has 2 divisors, whose sum is σ = 1256842130. Its totient is φ = 1256842128.

The previous prime is 1256842121. The next prime is 1256842133. The reversal of 1256842129 is 9212486521.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1004890000 + 251952129 = 31700^2 + 15873^2 .

It is a cyclic number.

It is not a de Polignac number, because 1256842129 - 2³ = 1256842121 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1256842091 and 1256842100.

It is not a weakly prime, because it can be changed into another prime (1256842121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 628421064 + 628421065.

It is an arithmetic number, because the mean of its divisors is an integer number (628421065).

Almost surely, 2^1256842129 is an apocalyptic number.

It is an amenable number.

1256842129 is a deficient number, since it is larger than the sum of its proper divisors (1).

1256842129 is an equidigital number, since it uses as much as digits as its factorization.

1256842129 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69120, while the sum is 40.

The square root of 1256842129 is about 35451.9693247075. The cubic root of 1256842129 is about 1079.1792257834.

The spelling of 1256842129 in words is "one billion, two hundred fifty-six million, eight hundred forty-two thousand, one hundred twenty-nine".