25864520661 has 24 divisors (see below), whose sum is σ = 43033196544. Its totient is φ = 14663345760.

The previous prime is 25864520657. The next prime is 25864520677. The reversal of 25864520661 is 16602546852.

25864520661 is a `hidden beast` number, since 2 + 5 + 8 + 64 + 520 + 6 + 61 = 666.

It is not a de Polignac number, because 25864520661 - 2² = 25864520657 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25864520641) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1608330 + ... + 1624331.

It is an arithmetic number, because the mean of its divisors is an integer number (1793049856).

Almost surely, 2^25864520661 is an apocalyptic number.

25864520661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

25864520661 is a deficient number, since it is larger than the sum of its proper divisors (17168675883).

25864520661 is a wasteful number, since it uses less digits than its factorization.

25864520661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3232801 (or 3232798 counting only the distinct ones).

The product of its (nonzero) digits is 691200, while the sum is 45.

The spelling of 25864520661 in words is "twenty-five billion, eight hundred sixty-four million, five hundred twenty thousand, six hundred sixty-one".