25691 has 4 divisors (see below), whose sum is σ = 26832. Its totient is φ = 24552.

The previous prime is 25679. The next prime is 25693. The reversal of 25691 is 19652.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-25691 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23), and also a Moran number because the ratio is a prime number: 1117 = 25691 / (2 + 5 + 6 + 9 + 1).

It is a Duffinian number.

It is a nialpdrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (25693) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 536 + ... + 581.

It is an arithmetic number, because the mean of its divisors is an integer number (6708).

2²⁵⁶⁹¹ is an apocalyptic number.

25691 is a deficient number, since it is larger than the sum of its proper divisors (1141).

25691 is a wasteful number, since it uses less digits than its factorization.

25691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1140.

The product of its digits is 540, while the sum is 23.

The square root of 25691 is about 160.2841227321. The cubic root of 25691 is about 29.5071322408.

The spelling of 25691 in words is "twenty-five thousand, six hundred ninety-one".