1256366991 has 16 divisors (see below), whose sum is σ = 1869943680. Its totient is φ = 743725920.

The previous prime is 1256366959. The next prime is 1256367037. The reversal of 1256366991 is 1996636521.

It is a happy number.

It is not a de Polignac number, because 1256366991 - 2⁵ = 1256366959 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1256366991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1256361991) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 441276 + ... + 444113.

It is an arithmetic number, because the mean of its divisors is an integer number (116871480).

Almost surely, 2^1256366991 is an apocalyptic number.

1256366991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1256366991 is a deficient number, since it is larger than the sum of its proper divisors (613576689).

1256366991 is a wasteful number, since it uses less digits than its factorization.

1256366991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 885446.

The product of its digits is 524880, while the sum is 48.

The square root of 1256366991 is about 35445.2675402514. The cubic root of 1256366991 is about 1079.0432172703.

The spelling of 1256366991 in words is "one billion, two hundred fifty-six million, three hundred sixty-six thousand, nine hundred ninety-one".