25717818521 has 2 divisors, whose sum is σ = 25717818522. Its totient is φ = 25717818520.

The previous prime is 25717818449. The next prime is 25717818583. The reversal of 25717818521 is 12581871752.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17686074121 + 8031744400 = 132989^2 + 89620^2 .

It is a cyclic number.

It is not a de Polignac number, because 25717818521 - 2¹⁸ = 25717556377 is a prime.

It is a super-2 number, since 2×25717818521² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (25717118521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12858909260 + 12858909261.

It is an arithmetic number, because the mean of its divisors is an integer number (12858909261).

Almost surely, 2^25717818521 is an apocalyptic number.

It is an amenable number.

25717818521 is a deficient number, since it is larger than the sum of its proper divisors (1).

25717818521 is an equidigital number, since it uses as much as digits as its factorization.

25717818521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 313600, while the sum is 47.

The spelling of 25717818521 in words is "twenty-five billion, seven hundred seventeen million, eight hundred eighteen thousand, five hundred twenty-one".