25481278561 has 4 divisors (see below), whose sum is σ = 26023433472. Its totient is φ = 24939123652.

The previous prime is 25481278541. The next prime is 25481278583. The reversal of 25481278561 is 16587218452.

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 25481278561 - 2⁹ = 25481278049 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25481278531) 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, 271077385 + ... + 271077478.

It is an arithmetic number, because the mean of its divisors is an integer number (6505858368).

Almost surely, 2^25481278561 is an apocalyptic number.

It is an amenable number.

25481278561 is a deficient number, since it is larger than the sum of its proper divisors (542154911).

25481278561 is an equidigital number, since it uses as much as digits as its factorization.

25481278561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 542154910.

The product of its digits is 1075200, while the sum is 49.

The spelling of 25481278561 in words is "twenty-five billion, four hundred eighty-one million, two hundred seventy-eight thousand, five hundred sixty-one".