257640217 has 4 divisors (see below), whose sum is σ = 260744400. Its totient is φ = 254536036.

The previous prime is 257640211. The next prime is 257640223. The reversal of 257640217 is 712046752.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (257640211) and next prime (257640223).

It is a cyclic number.

It is not a de Polignac number, because 257640217 - 2²⁷ = 123422489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (257640211) 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, 1551967 + ... + 1552132.

It is an arithmetic number, because the mean of its divisors is an integer number (65186100).

Almost surely, 2^257640217 is an apocalyptic number.

It is an amenable number.

257640217 is a deficient number, since it is larger than the sum of its proper divisors (3104183).

257640217 is an equidigital number, since it uses as much as digits as its factorization.

257640217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3104182.

The product of its (nonzero) digits is 23520, while the sum is 34.

The square root of 257640217 is about 16051.1749414178. The cubic root of 257640217 is about 636.3136193385.

Adding to 257640217 its reverse (712046752), we get a palindrome (969686969).

The spelling of 257640217 in words is "two hundred fifty-seven million, six hundred forty thousand, two hundred seventeen".