21111120001981 has 2 divisors, whose sum is σ = 21111120001982. Its totient is φ = 21111120001980.

The previous prime is 21111120001949. The next prime is 21111120002017. The reversal of 21111120001981 is 18910002111112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14068943237881 + 7042176764100 = 3750859^2 + 2653710^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111120001981 - 2⁵ = 21111120001949 is a prime.

It is a super-2 number, since 2×21111120001981² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111120001481) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555560000990 + 10555560000991.

It is an arithmetic number, because the mean of its divisors is an integer number (10555560000991).

Almost surely, 2^{21111120001981} is an apocalyptic number.

It is an amenable number.

21111120001981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111120001981 is an equidigital number, since it uses as much as digits as its factorization.

21111120001981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 28.

The spelling of 21111120001981 in words is "twenty-one trillion, one hundred eleven billion, one hundred twenty million, one thousand, nine hundred eighty-one".