211855818709 has 4 divisors (see below), whose sum is σ = 212033402316. Its totient is φ = 211678235104.

The previous prime is 211855818619. The next prime is 211855818737. The reversal of 211855818709 is 907818558112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 101168524900 + 110687293809 = 318070^2 + 332697^2 .

It is a cyclic number.

It is not a de Polignac number, because 211855818709 - 2¹⁹ = 211855294421 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 211855818709.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211855818509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 88790014 + ... + 88792399.

It is an arithmetic number, because the mean of its divisors is an integer number (53008350579).

Almost surely, 2^211855818709 is an apocalyptic number.

It is an amenable number.

211855818709 is a deficient number, since it is larger than the sum of its proper divisors (177583607).

211855818709 is a wasteful number, since it uses less digits than its factorization.

211855818709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177583606.

The product of its (nonzero) digits is 1612800, while the sum is 55.

The spelling of 211855818709 in words is "two hundred eleven billion, eight hundred fifty-five million, eight hundred eighteen thousand, seven hundred nine".