21251311 has 2 divisors, whose sum is σ = 21251312. Its totient is φ = 21251310.

The previous prime is 21251299. The next prime is 21251327. The reversal of 21251311 is 11315212.

It is an a-pointer prime, because the next prime (21251327) can be obtained adding 21251311 to its sum of digits (16).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21251311 - 2¹⁹ = 20727023 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21251381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10625655 + 10625656.

It is an arithmetic number, because the mean of its divisors is an integer number (10625656).

Almost surely, 2^21251311 is an apocalyptic number.

21251311 is a deficient number, since it is larger than the sum of its proper divisors (1).

21251311 is an equidigital number, since it uses as much as digits as its factorization.

21251311 is an evil number, because the sum of its binary digits is even.

The product of its digits is 60, while the sum is 16.

The square root of 21251311 is about 4609.9144243684. The cubic root of 21251311 is about 276.9886087927.

Adding to 21251311 its reverse (11315212), we get a palindrome (32566523).

The spelling of 21251311 in words is "twenty-one million, two hundred fifty-one thousand, three hundred eleven".