25218521 has 2 divisors, whose sum is σ = 25218522. Its totient is φ = 25218520.

The previous prime is 25218493. The next prime is 25218527. The reversal of 25218521 is 12581252.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23425600 + 1792921 = 4840^2 + 1339^2 .

It is a cyclic number.

It is not a de Polignac number, because 25218521 - 2¹⁸ = 24956377 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (25218527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12609260 + 12609261.

It is an arithmetic number, because the mean of its divisors is an integer number (12609261).

Almost surely, 2^25218521 is an apocalyptic number.

It is an amenable number.

25218521 is a deficient number, since it is larger than the sum of its proper divisors (1).

25218521 is an equidigital number, since it uses as much as digits as its factorization.

25218521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1600, while the sum is 26.

The square root of 25218521 is about 5021.8045561332. The cubic root of 25218521 is about 293.2512492718.

Adding to 25218521 its reverse (12581252), we get a palindrome (37799773).

It can be divided in two parts, 252185 and 21, that multiplied together give a triangular number (5295885 = T₃₂₅₄).

The spelling of 25218521 in words is "twenty-five million, two hundred eighteen thousand, five hundred twenty-one".