25661681 has 4 divisors (see below), whose sum is σ = 25696164. Its totient is φ = 25627200.

The previous prime is 25661677. The next prime is 25661717. The reversal of 25661681 is 18616652.

It is a happy number.

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 250000 + 25411681 = 500^2 + 5041^2 .

It is a cyclic number.

It is not a de Polignac number, because 25661681 - 2² = 25661677 is a prime.

It is a super-2 number, since 2×25661681² = 1317043743491522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25661611) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16100 + ... + 17621.

It is an arithmetic number, because the mean of its divisors is an integer number (6424041).

Almost surely, 2^25661681 is an apocalyptic number.

It is an amenable number.

25661681 is a deficient number, since it is larger than the sum of its proper divisors (34483).

25661681 is an equidigital number, since it uses as much as digits as its factorization.

25661681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34482.

The product of its digits is 17280, while the sum is 35.

The square root of 25661681 is about 5065.7359781181. The cubic root of 25661681 is about 294.9590329015.

The spelling of 25661681 in words is "twenty-five million, six hundred sixty-one thousand, six hundred eighty-one".