25661999 has 8 divisors (see below), whose sum is σ = 28151760. Its totient is φ = 23198400.

The previous prime is 25661981. The next prime is 25662037. The reversal of 25661999 is 99916652.

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

It is a cyclic number.

It is not a de Polignac number, because 25661999 - 2²⁰ = 24613423 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25661929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4454 + ... + 8435.

It is an arithmetic number, because the mean of its divisors is an integer number (3518970).

Almost surely, 2^25661999 is an apocalyptic number.

25661999 is a deficient number, since it is larger than the sum of its proper divisors (2489761).

25661999 is a wasteful number, since it uses less digits than its factorization.

25661999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13081.

The product of its digits is 262440, while the sum is 47.

The square root of 25661999 is about 5065.7673653653. The cubic root of 25661999 is about 294.9602512757.

The spelling of 25661999 in words is "twenty-five million, six hundred sixty-one thousand, nine hundred ninety-nine".