218780813 has 2 divisors, whose sum is σ = 218780814. Its totient is φ = 218780812.

The previous prime is 218780777. The next prime is 218780819. The reversal of 218780813 is 318087812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 201583204 + 17197609 = 14198^2 + 4147^2 .

It is a cyclic number.

It is not a de Polignac number, because 218780813 - 2¹⁰ = 218779789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218780819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109390406 + 109390407.

It is an arithmetic number, because the mean of its divisors is an integer number (109390407).

Almost surely, 2^218780813 is an apocalyptic number.

It is an amenable number.

218780813 is a deficient number, since it is larger than the sum of its proper divisors (1).

218780813 is an equidigital number, since it uses as much as digits as its factorization.

218780813 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 21504, while the sum is 38.

The square root of 218780813 is about 14791.2410905914. The cubic root of 218780813 is about 602.5638556541.

The spelling of 218780813 in words is "two hundred eighteen million, seven hundred eighty thousand, eight hundred thirteen".