25666721 has 4 divisors (see below), whose sum is σ = 25682052. Its totient is φ = 25651392.

The previous prime is 25666717. The next prime is 25666723. The reversal of 25666721 is 12766652.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16516096 + 9150625 = 4064^2 + 3025^2 .

It is a cyclic number.

It is not a de Polignac number, because 25666721 - 2² = 25666717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25666723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4796 + ... + 8621.

It is an arithmetic number, because the mean of its divisors is an integer number (6420513).

Almost surely, 2^25666721 is an apocalyptic number.

It is an amenable number.

25666721 is a deficient number, since it is larger than the sum of its proper divisors (15331).

25666721 is a wasteful number, since it uses less digits than its factorization.

25666721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15330.

The product of its digits is 30240, while the sum is 35.

The square root of 25666721 is about 5066.2334134937. The cubic root of 25666721 is about 294.9783417979.

The spelling of 25666721 in words is "twenty-five million, six hundred sixty-six thousand, seven hundred twenty-one".