211001981 has 2 divisors, whose sum is σ = 211001982. Its totient is φ = 211001980.

The previous prime is 211001971. The next prime is 211002013. The reversal of 211001981 is 189100112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 172685881 + 38316100 = 13141^2 + 6190^2 .

It is a cyclic number.

It is not a de Polignac number, because 211001981 - 2²² = 206807677 is a prime.

It is a super-2 number, since 2×211001981² = 89043671971848722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (211001911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 105500990 + 105500991.

It is an arithmetic number, because the mean of its divisors is an integer number (105500991).

Almost surely, 2^211001981 is an apocalyptic number.

It is an amenable number.

211001981 is a deficient number, since it is larger than the sum of its proper divisors (1).

211001981 is an equidigital number, since it uses as much as digits as its factorization.

211001981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 211001981 is about 14525.9072350060. The cubic root of 211001981 is about 595.3360444313.

The spelling of 211001981 in words is "two hundred eleven million, one thousand, nine hundred eighty-one".