25721021 has 4 divisors (see below), whose sum is σ = 25812192. Its totient is φ = 25629852.

The previous prime is 25721011. The next prime is 25721027. The reversal of 25721021 is 12012752.

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 a de Polignac number, because none of the positive numbers 2^k-25721021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 25720984 and 25721002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25721027) 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 3 ways as a sum of consecutive naturals, for example, 45161 + ... + 45726.

It is an arithmetic number, because the mean of its divisors is an integer number (6453048).

Almost surely, 2^25721021 is an apocalyptic number.

It is an amenable number.

25721021 is a deficient number, since it is larger than the sum of its proper divisors (91171).

25721021 is an equidigital number, since it uses as much as digits as its factorization.

25721021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91170.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 25721021 is about 5071.5895930172. The cubic root of 25721021 is about 295.1862120319.

Adding to 25721021 its reverse (12012752), we get a palindrome (37733773).

The spelling of 25721021 in words is "twenty-five million, seven hundred twenty-one thousand, twenty-one".