1256378781 has 32 divisors (see below), whose sum is σ = 2017715200. Its totient is φ = 679311360.

The previous prime is 1256378777. The next prime is 1256378797. The reversal of 1256378781 is 1878736521.

It is a happy number.

It is not a de Polignac number, because 1256378781 - 2² = 1256378777 is a prime.

It is a super-2 number, since 2×1256378781² = 3156975282694091922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1256378781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1256378731) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 465885 + ... + 468573.

It is an arithmetic number, because the mean of its divisors is an integer number (63053600).

Almost surely, 2^1256378781 is an apocalyptic number.

It is an amenable number.

1256378781 is a deficient number, since it is larger than the sum of its proper divisors (761336419).

1256378781 is a wasteful number, since it uses less digits than its factorization.

1256378781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3889.

The product of its digits is 564480, while the sum is 48.

The square root of 1256378781 is about 35445.4338526135. The cubic root of 1256378781 is about 1079.0465925791.

The spelling of 1256378781 in words is "one billion, two hundred fifty-six million, three hundred seventy-eight thousand, seven hundred eighty-one".