1256431981 has 48 divisors (see below), whose sum is σ = 1578864000. Its totient is φ = 999044928.

The previous prime is 1256431973. The next prime is 1256431993. The reversal of 1256431981 is 1891346521.

It is not a de Polignac number, because 1256431981 - 2³ = 1256431973 is a prime.

It is a super-2 number, since 2×1256431981² = 3157242645759168722, which contains 22 as substring.

It is a hoax number, since the sum of its digits (40) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1256431901) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 9039010 + ... + 9039148.

It is an arithmetic number, because the mean of its divisors is an integer number (32893000).

Almost surely, 2^1256431981 is an apocalyptic number.

It is an amenable number.

1256431981 is a deficient number, since it is larger than the sum of its proper divisors (322432019).

1256431981 is an equidigital number, since it uses as much as digits as its factorization.

1256431981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271 (or 238 counting only the distinct ones).

The product of its digits is 51840, while the sum is 40.

The square root of 1256431981 is about 35446.1842939406. The cubic root of 1256431981 is about 1079.0618227176.

The spelling of 1256431981 in words is "one billion, two hundred fifty-six million, four hundred thirty-one thousand, nine hundred eighty-one".