21311123 has 2 divisors, whose sum is σ = 21311124. Its totient is φ = 21311122.

The previous prime is 21311117. The next prime is 21311137. The reversal of 21311123 is 32111312.

It is an a-pointer prime, because the next prime (21311137) can be obtained adding 21311123 to its sum of digits (14).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21311123 - 2⁴ = 21311107 is a prime.

It is a super-2 number, since 2×21311123² = 908327927042258, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21311098 and 21311107.

It is not a weakly prime, because it can be changed into another prime (21311113) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655561 + 10655562.

It is an arithmetic number, because the mean of its divisors is an integer number (10655562).

Almost surely, 2^21311123 is an apocalyptic number.

21311123 is a deficient number, since it is larger than the sum of its proper divisors (1).

21311123 is an equidigital number, since it uses as much as digits as its factorization.

21311123 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36, while the sum is 14.

The square root of 21311123 is about 4616.3971882844. The cubic root of 21311123 is about 277.2482276627.

Adding to 21311123 its reverse (32111312), we get a palindrome (53422435).

The spelling of 21311123 in words is "twenty-one million, three hundred eleven thousand, one hundred twenty-three".