25666661 has 2 divisors, whose sum is σ = 25666662. Its totient is φ = 25666660.

The previous prime is 25666639. The next prime is 25666679. The reversal of 25666661 is 16666652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23961025 + 1705636 = 4895^2 + 1306^2 .

It is a cyclic number.

It is not a de Polignac number, because 25666661 - 2¹⁴ = 25650277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25666601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12833330 + 12833331.

It is an arithmetic number, because the mean of its divisors is an integer number (12833331).

Almost surely, 2^25666661 is an apocalyptic number.

It is an amenable number.

25666661 is a deficient number, since it is larger than the sum of its proper divisors (1).

25666661 is an equidigital number, since it uses as much as digits as its factorization.

25666661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 77760, while the sum is 38.

The square root of 25666661 is about 5066.2274919312. The cubic root of 25666661 is about 294.9781119449.

Subtracting from 25666661 its reverse (16666652), we obtain a palindrome (9000009).

The spelling of 25666661 in words is "twenty-five million, six hundred sixty-six thousand, six hundred sixty-one".