256399791 has 16 divisors (see below), whose sum is σ = 368240640. Its totient is φ = 158225760.

The previous prime is 256399783. The next prime is 256399799. The reversal of 256399791 is 197993652.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (256399783) and next prime (256399799).

It is not a de Polignac number, because 256399791 - 2³ = 256399783 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256399799) 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, 57796 + ... + 62073.

It is an arithmetic number, because the mean of its divisors is an integer number (23015040).

Almost surely, 2^256399791 is an apocalyptic number.

256399791 is a deficient number, since it is larger than the sum of its proper divisors (111840849).

256399791 is a wasteful number, since it uses less digits than its factorization.

256399791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119926.

The product of its digits is 918540, while the sum is 51.

The square root of 256399791 is about 16012.4885948437. The cubic root of 256399791 is about 635.2907846296.

The spelling of 256399791 in words is "two hundred fifty-six million, three hundred ninety-nine thousand, seven hundred ninety-one".