25640991 has 12 divisors (see below), whose sum is σ = 37825632. Its totient is φ = 16730016.

The previous prime is 25640983. The next prime is 25641047. The reversal of 25640991 is 19904652.

25640991 is a `hidden beast` number, since 2 + 5 + 640 + 9 + 9 + 1 = 666.

It is not a de Polignac number, because 25640991 - 2³ = 25640983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25640921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29886 + ... + 30731.

It is an arithmetic number, because the mean of its divisors is an integer number (3152136).

Almost surely, 2^25640991 is an apocalyptic number.

25640991 is a deficient number, since it is larger than the sum of its proper divisors (12184641).

25640991 is a wasteful number, since it uses less digits than its factorization.

25640991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60670 (or 60667 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 25640991 is about 5063.6934148900. The cubic root of 25640991 is about 294.8797403142.

The spelling of 25640991 in words is "twenty-five million, six hundred forty thousand, nine hundred ninety-one".