25640209 has 4 divisors (see below), whose sum is σ = 29303104. Its totient is φ = 21977316.

The previous prime is 25640207. The next prime is 25640213. The reversal of 25640209 is 90204652.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 25640209 - 2¹ = 25640207 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25640201) 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, 1831437 + ... + 1831450.

It is an arithmetic number, because the mean of its divisors is an integer number (7325776).

Almost surely, 2^25640209 is an apocalyptic number.

It is an amenable number.

25640209 is a deficient number, since it is larger than the sum of its proper divisors (3662895).

25640209 is an equidigital number, since it uses as much as digits as its factorization.

25640209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3662894.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 25640209 is about 5063.6161979360. The cubic root of 25640209 is about 294.8767425322.

The spelling of 25640209 in words is "twenty-five million, six hundred forty thousand, two hundred nine".