21681113 has 2 divisors, whose sum is σ = 21681114. Its totient is φ = 21681112.

The previous prime is 21681097. The next prime is 21681151. The reversal of 21681113 is 31118612.

21681113 = 3292² + 3293².

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10843849 + 10837264 = 3293^2 + 3292^2 .

It is a cyclic number.

It is not a de Polignac number, because 21681113 - 2⁴ = 21681097 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21681173) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10840556 + 10840557.

It is an arithmetic number, because the mean of its divisors is an integer number (10840557).

Almost surely, 2^21681113 is an apocalyptic number.

21681113 is the 3293-rd centered square number.

It is an amenable number.

21681113 is a deficient number, since it is larger than the sum of its proper divisors (1).

21681113 is an equidigital number, since it uses as much as digits as its factorization.

21681113 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 23.

The square root of 21681113 is about 4656.2982078041. The cubic root of 21681113 is about 278.8434993712.

Adding to 21681113 its reverse (31118612), we get a palindrome (52799725).

The spelling of 21681113 in words is "twenty-one million, six hundred eighty-one thousand, one hundred thirteen".