211906981 has 32 divisors (see below), whose sum is σ = 273530880. Its totient is φ = 161092800.

The previous prime is 211906969. The next prime is 211906987. The reversal of 211906981 is 189609112.

It is not a de Polignac number, because 211906981 - 2⁵ = 211906949 is a prime.

It is a super-2 number, since 2×211906981² = 89809137193068722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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 211906981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211906987) 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 in 31 ways as a sum of consecutive naturals, for example, 60796 + ... + 64186.

It is an arithmetic number, because the mean of its divisors is an integer number (8547840).

Almost surely, 2^211906981 is an apocalyptic number.

It is an amenable number.

211906981 is a deficient number, since it is larger than the sum of its proper divisors (61623899).

211906981 is a wasteful number, since it uses less digits than its factorization.

211906981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3457.

The product of its (nonzero) digits is 7776, while the sum is 37.

The square root of 211906981 is about 14557.0251425214. The cubic root of 211906981 is about 596.1859743114.

The spelling of 211906981 in words is "two hundred eleven million, nine hundred six thousand, nine hundred eighty-one".