21111121111261 has 2 divisors, whose sum is σ = 21111121111262. Its totient is φ = 21111121111260.

The previous prime is 21111121111243. The next prime is 21111121111277. The reversal of 21111121111261 is 16211112111112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11551120905636 + 9560000205625 = 3398694^2 + 3091925^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111121111261 - 2⁹ = 21111121110749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111121111291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555560555630 + 10555560555631.

It is an arithmetic number, because the mean of its divisors is an integer number (10555560555631).

Almost surely, 2^{21111121111261} is an apocalyptic number.

It is an amenable number.

21111121111261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111121111261 is an equidigital number, since it uses as much as digits as its factorization.

21111121111261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 48, while the sum is 22.

Adding to 21111121111261 its reverse (16211112111112), we get a palindrome (37322233222373).

The spelling of 21111121111261 in words is "twenty-one trillion, one hundred eleven billion, one hundred twenty-one million, one hundred eleven thousand, two hundred sixty-one".