25440021 has 8 divisors (see below), whose sum is σ = 37688960. Its totient is φ = 16959996.

The previous prime is 25440013. The next prime is 25440043. The reversal of 25440021 is 12004452.

It is not a de Polignac number, because 25440021 - 2³ = 25440013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 25439976 and 25440003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25440011) 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 7 ways as a sum of consecutive naturals, for example, 471085 + ... + 471138.

It is an arithmetic number, because the mean of its divisors is an integer number (4711120).

Almost surely, 2^25440021 is an apocalyptic number.

It is an amenable number.

25440021 is a deficient number, since it is larger than the sum of its proper divisors (12248939).

25440021 is an equidigital number, since it uses as much as digits as its factorization.

25440021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 942232 (or 942226 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 25440021 is about 5043.8101669274. The cubic root of 25440021 is about 294.1073119294.

Adding to 25440021 its reverse (12004452), we get a palindrome (37444473).

The spelling of 25440021 in words is "twenty-five million, four hundred forty thousand, twenty-one".