21255257869 has 2 divisors, whose sum is σ = 21255257870. Its totient is φ = 21255257868.

The previous prime is 21255257741. The next prime is 21255257893. The reversal of 21255257869 is 96875255212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15393364900 + 5861892969 = 124070^2 + 76563^2 .

It is a cyclic number.

It is not a de Polignac number, because 21255257869 - 2⁷ = 21255257741 is a prime.

It is a super-2 number, since 2×21255257869² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21255257899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10627628934 + 10627628935.

It is an arithmetic number, because the mean of its divisors is an integer number (10627628935).

Almost surely, 2^21255257869 is an apocalyptic number.

It is an amenable number.

21255257869 is a deficient number, since it is larger than the sum of its proper divisors (1).

21255257869 is an equidigital number, since it uses as much as digits as its factorization.

21255257869 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024000, while the sum is 52.

The spelling of 21255257869 in words is "twenty-one billion, two hundred fifty-five million, two hundred fifty-seven thousand, eight hundred sixty-nine".