66401521 has 2 divisors, whose sum is σ = 66401522. Its totient is φ = 66401520.

The previous prime is 66401501. The next prime is 66401539. The reversal of 66401521 is 12510466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66194496 + 207025 = 8136^2 + 455^2 .

It is a cyclic number.

It is not a de Polignac number, because 66401521 - 2⁹ = 66401009 is a prime.

It is a super-2 number, since 2×66401521² = 8818323982226882, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (66401501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33200760 + 33200761.

It is an arithmetic number, because the mean of its divisors is an integer number (33200761).

Almost surely, 2^66401521 is an apocalyptic number.

It is an amenable number.

66401521 is a deficient number, since it is larger than the sum of its proper divisors (1).

66401521 is an equidigital number, since it uses as much as digits as its factorization.

66401521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 66401521 is about 8148.7128431428. The cubic root of 66401521 is about 404.9418623045.

Adding to 66401521 its reverse (12510466), we get a palindrome (78911987).

The spelling of 66401521 in words is "sixty-six million, four hundred one thousand, five hundred twenty-one".