1256109157 has 4 divisors (see below), whose sum is σ = 1256251360. Its totient is φ = 1255966956.

The previous prime is 1256109149. The next prime is 1256109167. The reversal of 1256109157 is 7519016521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7519016521 = 313 ⋅24022417.

It is a cyclic number.

It is not a de Polignac number, because 1256109157 - 2³ = 1256109149 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1256109167) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 56907 + ... + 75832.

It is an arithmetic number, because the mean of its divisors is an integer number (314062840).

Almost surely, 2^1256109157 is an apocalyptic number.

It is an amenable number.

1256109157 is a deficient number, since it is larger than the sum of its proper divisors (142203).

1256109157 is an equidigital number, since it uses as much as digits as its factorization.

1256109157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142202.

The product of its (nonzero) digits is 18900, while the sum is 37.

The square root of 1256109157 is about 35441.6302813513. The cubic root of 1256109157 is about 1078.9693977932.

The spelling of 1256109157 in words is "one billion, two hundred fifty-six million, one hundred nine thousand, one hundred fifty-seven".