21001211111 has 2 divisors, whose sum is σ = 21001211112. Its totient is φ = 21001211110.

The previous prime is 21001211093. The next prime is 21001211261. The reversal of 21001211111 is 11111210012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21001211111 - 2⁶ = 21001211047 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001211092 and 21001211101.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21001211311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500605555 + 10500605556.

It is an arithmetic number, because the mean of its divisors is an integer number (10500605556).

Almost surely, 2^21001211111 is an apocalyptic number.

21001211111 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001211111 is an equidigital number, since it uses as much as digits as its factorization.

21001211111 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4, while the sum is 11.

Adding to 21001211111 its reverse (11111210012), we get a palindrome (32112421123).

It can be divided in two parts, 210012 and 11111, that multiplied together give a palindrome (2333443332).

The spelling of 21001211111 in words is "twenty-one billion, one million, two hundred eleven thousand, one hundred eleven".