216638791 has 2 divisors, whose sum is σ = 216638792. Its totient is φ = 216638790.

The previous prime is 216638753. The next prime is 216638827. The reversal of 216638791 is 197836612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 216638791 - 2²⁷ = 82421063 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216638291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108319395 + 108319396.

It is an arithmetic number, because the mean of its divisors is an integer number (108319396).

Almost surely, 2^216638791 is an apocalyptic number.

216638791 is a deficient number, since it is larger than the sum of its proper divisors (1).

216638791 is an equidigital number, since it uses as much as digits as its factorization.

216638791 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 43.

The square root of 216638791 is about 14718.6545241065. The cubic root of 216638791 is about 600.5908910368.

The spelling of 216638791 in words is "two hundred sixteen million, six hundred thirty-eight thousand, seven hundred ninety-one".