25166231821 has 2 divisors, whose sum is σ = 25166231822. Its totient is φ = 25166231820.

The previous prime is 25166231819. The next prime is 25166231869. The reversal of 25166231821 is 12813266152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 25150470921 + 15760900 = 158589^2 + 3970^2 .

It is a cyclic number.

It is not a de Polignac number, because 25166231821 - 2¹ = 25166231819 is a prime.

Together with 25166231819, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25166231221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12583115910 + 12583115911.

It is an arithmetic number, because the mean of its divisors is an integer number (12583115911).

Almost surely, 2^25166231821 is an apocalyptic number.

It is an amenable number.

25166231821 is a deficient number, since it is larger than the sum of its proper divisors (1).

25166231821 is an equidigital number, since it uses as much as digits as its factorization.

25166231821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34560, while the sum is 37.

Adding to 25166231821 its reverse (12813266152), we get a palindrome (37979497973).

The spelling of 25166231821 in words is "twenty-five billion, one hundred sixty-six million, two hundred thirty-one thousand, eight hundred twenty-one".