1256489809 has 3 divisors (see below), whose sum is σ = 1256525257. Its totient is φ = 1256454362.

The previous prime is 1256489723. The next prime is 1256489833. The reversal of 1256489809 is 9089846521.

The square root of 1256489809 is 35447.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 9089846521 = 7 ⋅1298549503.

It is not a de Polignac number, because 1256489809 - 2¹⁹ = 1255965521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1256489849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 17724 + ... + 53170.

Almost surely, 2^1256489809 is an apocalyptic number.

1256489809 is the 35447-th square number.

1256489809 is the 17724-th centered octagonal number.

It is an amenable number.

1256489809 is a deficient number, since it is larger than the sum of its proper divisors (35448).

1256489809 is an frugal number, since it uses more digits than its factorization.

1256489809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70894 (or 35447 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 52.

The cubic root of 1256489809 is about 1079.0783772760.

The spelling of 1256489809 in words is "one billion, two hundred fifty-six million, four hundred eighty-nine thousand, eight hundred nine".