21051913 has 2 divisors, whose sum is σ = 21051914. Its totient is φ = 21051912.

The previous prime is 21051907. The next prime is 21051949. The reversal of 21051913 is 31915012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14040009 + 7011904 = 3747^2 + 2648^2 .

It is a cyclic number.

It is not a de Polignac number, because 21051913 - 2¹⁷ = 20920841 is a prime.

It is not a weakly prime, because it can be changed into another prime (21091913) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10525956 + 10525957.

It is an arithmetic number, because the mean of its divisors is an integer number (10525957).

Almost surely, 2^21051913 is an apocalyptic number.

It is an amenable number.

21051913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21051913 is an equidigital number, since it uses as much as digits as its factorization.

21051913 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 270, while the sum is 22.

The square root of 21051913 is about 4588.2363714177. The cubic root of 21051913 is about 276.1195702948.

Adding to 21051913 its reverse (31915012), we get a palindrome (52966925).

The spelling of 21051913 in words is "twenty-one million, fifty-one thousand, nine hundred thirteen".