211997861 has 2 divisors, whose sum is σ = 211997862. Its totient is φ = 211997860.

The previous prime is 211997857. The next prime is 211997881. The reversal of 211997861 is 168799112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 202350625 + 9647236 = 14225^2 + 3106^2 .

It is a cyclic number.

It is not a de Polignac number, because 211997861 - 2² = 211997857 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (211997881) 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, 105998930 + 105998931.

It is an arithmetic number, because the mean of its divisors is an integer number (105998931).

Almost surely, 2^211997861 is an apocalyptic number.

It is an amenable number.

211997861 is a deficient number, since it is larger than the sum of its proper divisors (1).

211997861 is an equidigital number, since it uses as much as digits as its factorization.

211997861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432, while the sum is 44.

The square root of 211997861 is about 14560.1463248142. The cubic root of 211997861 is about 596.2711903771.

The spelling of 211997861 in words is "two hundred eleven million, nine hundred ninety-seven thousand, eight hundred sixty-one".