25666803509 has 2 divisors, whose sum is σ = 25666803510. Its totient is φ = 25666803508.

The previous prime is 25666803413. The next prime is 25666803511. The reversal of 25666803509 is 90530866652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19162864900 + 6503938609 = 138430^2 + 80647^2 .

It is a cyclic number.

It is not a de Polignac number, because 25666803509 - 2¹² = 25666799413 is a prime.

It is a super-2 number, since 2×25666803509² (a number of 22 digits) contains 22 as substring.

Together with 25666803511, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25666803529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12833401754 + 12833401755.

It is an arithmetic number, because the mean of its divisors is an integer number (12833401755).

Almost surely, 2^25666803509 is an apocalyptic number.

It is an amenable number.

25666803509 is a deficient number, since it is larger than the sum of its proper divisors (1).

25666803509 is an equidigital number, since it uses as much as digits as its factorization.

25666803509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2332800, while the sum is 50.

The spelling of 25666803509 in words is "twenty-five billion, six hundred sixty-six million, eight hundred three thousand, five hundred nine".