25721 has 6 divisors (see below), whose sum is σ = 27630. Its totient is φ = 23936.

The previous prime is 25717. The next prime is 25733. The reversal of 25721 is 12752.

It can be written as a sum of positive squares in 3 ways, for example, as 6400 + 19321 = 80^2 + 139^2 .

It is not a de Polignac number, because 25721 - 2² = 25717 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Duffinian number.

It is a nialpdrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 25721.

It is not an unprimeable number, because it can be changed into a prime (25741) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 245 + ... + 333.

It is an arithmetic number, because the mean of its divisors is an integer number (4605).

2²⁵⁷²¹ is an apocalyptic number.

It is an amenable number.

25721 is a deficient number, since it is larger than the sum of its proper divisors (1909).

25721 is an equidigital number, since it uses as much as digits as its factorization.

25721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123 (or 106 counting only the distinct ones).

The product of its digits is 140, while the sum is 17.

The square root of 25721 is about 160.3776792450. The cubic root of 25721 is about 29.5186131697.

The spelling of 25721 in words is "twenty-five thousand, seven hundred twenty-one".