21006311 has 2 divisors, whose sum is σ = 21006312. Its totient is φ = 21006310.

The previous prime is 21006289. The next prime is 21006329. The reversal of 21006311 is 11360012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21006311 - 2⁶ = 21006247 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21006341) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503155 + 10503156.

It is an arithmetic number, because the mean of its divisors is an integer number (10503156).

Almost surely, 2^21006311 is an apocalyptic number.

21006311 is a deficient number, since it is larger than the sum of its proper divisors (1).

21006311 is an equidigital number, since it uses as much as digits as its factorization.

21006311 is an evil number, because the sum of its binary digits is even.

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

The square root of 21006311 is about 4583.2642297821. The cubic root of 21006311 is about 275.9200522835.

Adding to 21006311 its reverse (11360012), we get a palindrome (32366323).

The spelling of 21006311 in words is "twenty-one million, six thousand, three hundred eleven".