25491864581 has 8 divisors (see below), whose sum is σ = 26674813944. Its totient is φ = 24334914240.

The previous prime is 25491864569. The next prime is 25491864583. The reversal of 25491864581 is 18546819452.

It can be written as a sum of positive squares in 4 ways, for example, as 10643223556 + 14848641025 = 103166^2 + 121855^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 25491864581 - 2¹⁰ = 25491863557 is a prime.

It is a super-2 number, since 2×25491864581² (a number of 22 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (53).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25491864583) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6497750 + ... + 6501671.

It is an arithmetic number, because the mean of its divisors is an integer number (3334351743).

Almost surely, 2^25491864581 is an apocalyptic number.

It is an amenable number.

25491864581 is a deficient number, since it is larger than the sum of its proper divisors (1182949363).

25491864581 is a wasteful number, since it uses less digits than its factorization.

25491864581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12999511.

The product of its digits is 2764800, while the sum is 53.

The spelling of 25491864581 in words is "twenty-five billion, four hundred ninety-one million, eight hundred sixty-four thousand, five hundred eighty-one".