256715217 has 16 divisors (see below), whose sum is σ = 414893760. Its totient is φ = 155584800.

The previous prime is 256715209. The next prime is 256715233. The reversal of 256715217 is 712517652.

It is not a de Polignac number, because 256715217 - 2³ = 256715209 is a prime.

It is not an unprimeable number, because it can be changed into a prime (256715297) 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, 431884 + ... + 432477.

It is an arithmetic number, because the mean of its divisors is an integer number (25930860).

Almost surely, 2^256715217 is an apocalyptic number.

256715217 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

256715217 is a deficient number, since it is larger than the sum of its proper divisors (158178543).

256715217 is a wasteful number, since it uses less digits than its factorization.

256715217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 864381 (or 864375 counting only the distinct ones).

The product of its digits is 29400, while the sum is 36.

The square root of 256715217 is about 16022.3349421987. The cubic root of 256715217 is about 635.5511919067.

The spelling of 256715217 in words is "two hundred fifty-six million, seven hundred fifteen thousand, two hundred seventeen".