25661521 has 4 divisors (see below), whose sum is σ = 26489344. Its totient is φ = 24833700.

The previous prime is 25661513. The next prime is 25661527. The reversal of 25661521 is 12516652.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 25661521 - 2³ = 25661513 is a prime.

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 25661521.

It is not an unprimeable number, because it can be changed into a prime (25661527) 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, 413865 + ... + 413926.

It is an arithmetic number, because the mean of its divisors is an integer number (6622336).

Almost surely, 2^25661521 is an apocalyptic number.

It is an amenable number.

25661521 is a deficient number, since it is larger than the sum of its proper divisors (827823).

25661521 is an equidigital number, since it uses as much as digits as its factorization.

25661521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 827822.

The product of its digits is 3600, while the sum is 28.

The square root of 25661521 is about 5065.7201857189. The cubic root of 25661521 is about 294.9584198793.

The spelling of 25661521 in words is "twenty-five million, six hundred sixty-one thousand, five hundred twenty-one".