25721161701665 has 8 divisors (see below), whose sum is σ = 30878623972008. Its totient is φ = 20568109408000.

The previous prime is 25721161701647. The next prime is 25721161701667. The reversal of 25721161701665 is 56610716112752.

It can be written as a sum of positive squares in 4 ways, for example, as 2786525765521 + 22934635936144 = 1669289^2 + 4789012^2 .

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

It is not a de Polignac number, because 25721161701665 - 2⁶ = 25721161701601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25721161701667) 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, 1102481336 + ... + 1102504665.

It is an arithmetic number, because the mean of its divisors is an integer number (3859827996501).

Almost surely, 2^{25721161701665} is an apocalyptic number.

It is an amenable number.

25721161701665 is a deficient number, since it is larger than the sum of its proper divisors (5157462270343).

25721161701665 is a wasteful number, since it uses less digits than its factorization.

25721161701665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2204988339.

The product of its (nonzero) digits is 1058400, while the sum is 50.

The spelling of 25721161701665 in words is "twenty-five trillion, seven hundred twenty-one billion, one hundred sixty-one million, seven hundred one thousand, six hundred sixty-five".