257215691 has 2 divisors, whose sum is σ = 257215692. Its totient is φ = 257215690.

The previous prime is 257215681. The next prime is 257215733. The reversal of 257215691 is 196512752.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 257215691 - 2¹⁸ = 256953547 is a prime.

It is not a weakly prime, because it can be changed into another prime (257215681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128607845 + 128607846.

It is an arithmetic number, because the mean of its divisors is an integer number (128607846).

Almost surely, 2^257215691 is an apocalyptic number.

257215691 is a deficient number, since it is larger than the sum of its proper divisors (1).

257215691 is an equidigital number, since it uses as much as digits as its factorization.

257215691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37800, while the sum is 38.

The square root of 257215691 is about 16037.9453484541. The cubic root of 257215691 is about 635.9639324971.

The spelling of 257215691 in words is "two hundred fifty-seven million, two hundred fifteen thousand, six hundred ninety-one".