21280757 has 2 divisors, whose sum is σ = 21280758. Its totient is φ = 21280756.

The previous prime is 21280747. The next prime is 21280771. The reversal of 21280757 is 75708212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21169201 + 111556 = 4601^2 + 334^2 .

It is a cyclic number.

It is not a de Polignac number, because 21280757 - 2¹⁶ = 21215221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21280747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10640378 + 10640379.

It is an arithmetic number, because the mean of its divisors is an integer number (10640379).

Almost surely, 2^21280757 is an apocalyptic number.

It is an amenable number.

21280757 is a deficient number, since it is larger than the sum of its proper divisors (1).

21280757 is an equidigital number, since it uses as much as digits as its factorization.

21280757 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7840, while the sum is 32.

The square root of 21280757 is about 4613.1070874195. The cubic root of 21280757 is about 277.1164823526.

Adding to 21280757 its reverse (75708212), we get a palindrome (96988969).

The spelling of 21280757 in words is "twenty-one million, two hundred eighty thousand, seven hundred fifty-seven".