25728221 has 2 divisors, whose sum is σ = 25728222. Its totient is φ = 25728220.

The previous prime is 25728211. The next prime is 25728229. The reversal of 25728221 is 12282752.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 25351225 + 376996 = 5035^2 + 614^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-25728221 is a prime.

It is equal to p_1608554 and since 25728221 and 1608554 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25728229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12864110 + 12864111.

It is an arithmetic number, because the mean of its divisors is an integer number (12864111).

Almost surely, 2^25728221 is an apocalyptic number.

It is an amenable number.

25728221 is a deficient number, since it is larger than the sum of its proper divisors (1).

25728221 is an equidigital number, since it uses as much as digits as its factorization.

25728221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4480, while the sum is 29.

The square root of 25728221 is about 5072.2993799657. The cubic root of 25728221 is about 295.2137529610.

The spelling of 25728221 in words is "twenty-five million, seven hundred twenty-eight thousand, two hundred twenty-one".