256843721 has 4 divisors (see below), whose sum is σ = 263108244. Its totient is φ = 250579200.

The previous prime is 256843703. The next prime is 256843771. The reversal of 256843721 is 127348652.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 80910025 + 175933696 = 8995^2 + 13264^2 .

It is a cyclic number.

It is not a de Polignac number, because 256843721 - 2²² = 252649417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256843771) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3132200 + ... + 3132281.

It is an arithmetic number, because the mean of its divisors is an integer number (65777061).

Almost surely, 2^256843721 is an apocalyptic number.

It is an amenable number.

256843721 is a deficient number, since it is larger than the sum of its proper divisors (6264523).

256843721 is an equidigital number, since it uses as much as digits as its factorization.

256843721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6264522.

The product of its digits is 80640, while the sum is 38.

The square root of 256843721 is about 16026.3445925763. The cubic root of 256843721 is about 635.6572202231.

The spelling of 256843721 in words is "two hundred fifty-six million, eight hundred forty-three thousand, seven hundred twenty-one".