218388857 has 2 divisors, whose sum is σ = 218388858. Its totient is φ = 218388856.

The previous prime is 218388809. The next prime is 218388871. The reversal of 218388857 is 758883812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 189915961 + 28472896 = 13781^2 + 5336^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218388857 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (218388557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109194428 + 109194429.

It is an arithmetic number, because the mean of its divisors is an integer number (109194429).

Almost surely, 2^218388857 is an apocalyptic number.

It is an amenable number.

218388857 is a deficient number, since it is larger than the sum of its proper divisors (1).

218388857 is an equidigital number, since it uses as much as digits as its factorization.

218388857 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 860160, while the sum is 50.

The square root of 218388857 is about 14777.9855528418. The cubic root of 218388857 is about 602.2038001606.

The spelling of 218388857 in words is "two hundred eighteen million, three hundred eighty-eight thousand, eight hundred fifty-seven".