25665821 has 2 divisors, whose sum is σ = 25665822. Its totient is φ = 25665820.

The previous prime is 25665793. The next prime is 25665823. The reversal of 25665821 is 12856652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 25140196 + 525625 = 5014^2 + 725^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-25665821 is a prime.

Together with 25665823, 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 (25665823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12832910 + 12832911.

It is an arithmetic number, because the mean of its divisors is an integer number (12832911).

Almost surely, 2^25665821 is an apocalyptic number.

It is an amenable number.

25665821 is a deficient number, since it is larger than the sum of its proper divisors (1).

25665821 is an equidigital number, since it uses as much as digits as its factorization.

25665821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 28800, while the sum is 35.

The square root of 25665821 is about 5066.1445893302. The cubic root of 25665821 is about 294.9748939661.

The spelling of 25665821 in words is "twenty-five million, six hundred sixty-five thousand, eight hundred twenty-one".