25605991 has 4 divisors (see below), whose sum is σ = 25956832. Its totient is φ = 25255152.

The previous prime is 25605989. The next prime is 25605997. The reversal of 25605991 is 19950652.

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

It is a cyclic number.

It is not a de Polignac number, because 25605991 - 2¹ = 25605989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 25605991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25605997) 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, 175311 + ... + 175456.

It is an arithmetic number, because the mean of its divisors is an integer number (6489208).

Almost surely, 2^25605991 is an apocalyptic number.

25605991 is a deficient number, since it is larger than the sum of its proper divisors (350841).

25605991 is an equidigital number, since it uses as much as digits as its factorization.

25605991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350840.

The product of its (nonzero) digits is 24300, while the sum is 37.

The square root of 25605991 is about 5060.2362593065. The cubic root of 25605991 is about 294.7455087571.

The spelling of 25605991 in words is "twenty-five million, six hundred five thousand, nine hundred ninety-one".