1256512421 has 2 divisors, whose sum is σ = 1256512422. Its totient is φ = 1256512420.

The previous prime is 1256512403. The next prime is 1256512423. The reversal of 1256512421 is 1242156521.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 955489921 + 301022500 = 30911^2 + 17350^2 .

It is a cyclic number.

It is not a de Polignac number, because 1256512421 - 2²² = 1252318117 is a prime.

Together with 1256512423, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1256512423) 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 as a sum of consecutive naturals, namely, 628256210 + 628256211.

It is an arithmetic number, because the mean of its divisors is an integer number (628256211).

Almost surely, 2^1256512421 is an apocalyptic number.

It is an amenable number.

1256512421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1256512421 is an equidigital number, since it uses as much as digits as its factorization.

1256512421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4800, while the sum is 29.

The square root of 1256512421 is about 35447.3189536247. The cubic root of 1256512421 is about 1079.0848503286.

Adding to 1256512421 its reverse (1242156521), we get a palindrome (2498668942).

The spelling of 1256512421 in words is "one billion, two hundred fifty-six million, five hundred twelve thousand, four hundred twenty-one".