25691221 has 2 divisors, whose sum is σ = 25691222. Its totient is φ = 25691220.

The previous prime is 25691201. The next prime is 25691261. The reversal of 25691221 is 12219652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16112196 + 9579025 = 4014^2 + 3095^2 .

It is a cyclic number.

It is not a de Polignac number, because 25691221 - 2¹³ = 25683029 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 25691221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25691201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12845610 + 12845611.

It is an arithmetic number, because the mean of its divisors is an integer number (12845611).

Almost surely, 2^25691221 is an apocalyptic number.

It is an amenable number.

25691221 is a deficient number, since it is larger than the sum of its proper divisors (1).

25691221 is an equidigital number, since it uses as much as digits as its factorization.

25691221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 28.

The square root of 25691221 is about 5068.6508066743. The cubic root of 25691221 is about 295.0721684967.

The spelling of 25691221 in words is "twenty-five million, six hundred ninety-one thousand, two hundred twenty-one".