15525221 has 2 divisors, whose sum is σ = 15525222. Its totient is φ = 15525220.

The previous prime is 15525157. The next prime is 15525229. The reversal of 15525221 is 12252551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11464996 + 4060225 = 3386^2 + 2015^2 .

It is an emirp because it is prime and its reverse (12252551) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15525221 - 2⁶ = 15525157 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15525229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7762610 + 7762611.

It is an arithmetic number, because the mean of its divisors is an integer number (7762611).

Almost surely, 2^15525221 is an apocalyptic number.

It is an amenable number.

15525221 is a deficient number, since it is larger than the sum of its proper divisors (1).

15525221 is an equidigital number, since it uses as much as digits as its factorization.

15525221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1000, while the sum is 23.

The square root of 15525221 is about 3940.2057052900. The cubic root of 15525221 is about 249.4667085431.

Adding to 15525221 its reverse (12252551), we get a palindrome (27777772).

The spelling of 15525221 in words is "fifteen million, five hundred twenty-five thousand, two hundred twenty-one".