25661521656 has 128 divisors (see below), whose sum is σ = 72726984000. Its totient is φ = 8382173184.

The previous prime is 25661521603. The next prime is 25661521667. The reversal of 25661521656 is 65612516652.

25661521656 is a `hidden beast` number, since 2 + 5 + 6 + 61 + 521 + 65 + 6 = 666.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2166406 + ... + 2178218.

Almost surely, 2^25661521656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 25661521656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36363492000).

25661521656 is an abundant number, since it is smaller than the sum of its proper divisors (47065462344).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

25661521656 is a wasteful number, since it uses less digits than its factorization.

25661521656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12030 (or 12020 counting only the distinct ones).

The product of its digits is 648000, while the sum is 45.

The spelling of 25661521656 in words is "twenty-five billion, six hundred sixty-one million, five hundred twenty-one thousand, six hundred fifty-six".