25651981 has 4 divisors (see below), whose sum is σ = 26003452. Its totient is φ = 25300512.

The previous prime is 25651943. The next prime is 25651987. The reversal of 25651981 is 18915652.

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 21068100 + 4583881 = 4590^2 + 2141^2 .

It is a cyclic number.

It is not a de Polignac number, because 25651981 - 2¹⁵ = 25619213 is a prime.

It is a super-2 number, since 2×25651981² = 1316048258448722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 25651981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25651987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 175626 + ... + 175771.

It is an arithmetic number, because the mean of its divisors is an integer number (6500863).

Almost surely, 2^25651981 is an apocalyptic number.

It is an amenable number.

25651981 is a deficient number, since it is larger than the sum of its proper divisors (351471).

25651981 is an equidigital number, since it uses as much as digits as its factorization.

25651981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351470.

The product of its digits is 21600, while the sum is 37.

The square root of 25651981 is about 5064.7784749187. The cubic root of 25651981 is about 294.9218638220.

The spelling of 25651981 in words is "twenty-five million, six hundred fifty-one thousand, nine hundred eighty-one".