21108757 has 2 divisors, whose sum is σ = 21108758. Its totient is φ = 21108756.

The previous prime is 21108751. The next prime is 21108793. The reversal of 21108757 is 75780112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16273156 + 4835601 = 4034^2 + 2199^2 .

It is a cyclic number.

It is not a de Polignac number, because 21108757 - 2³ = 21108749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21108751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10554378 + 10554379.

It is an arithmetic number, because the mean of its divisors is an integer number (10554379).

Almost surely, 2^21108757 is an apocalyptic number.

It is an amenable number.

21108757 is a deficient number, since it is larger than the sum of its proper divisors (1).

21108757 is an equidigital number, since it uses as much as digits as its factorization.

21108757 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3920, while the sum is 31.

The square root of 21108757 is about 4594.4267324662. The cubic root of 21108757 is about 276.3678713223.

Adding to 21108757 its reverse (75780112), we get a palindrome (96888869).

The spelling of 21108757 in words is "twenty-one million, one hundred eight thousand, seven hundred fifty-seven".