66521573 has 2 divisors, whose sum is σ = 66521574. Its totient is φ = 66521572.

The previous prime is 66521551. The next prime is 66521599. The reversal of 66521573 is 37512566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 52519009 + 14002564 = 7247^2 + 3742^2 .

It is a cyclic number.

It is not a de Polignac number, because 66521573 - 2⁶ = 66521509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66521513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33260786 + 33260787.

It is an arithmetic number, because the mean of its divisors is an integer number (33260787).

Almost surely, 2^66521573 is an apocalyptic number.

It is an amenable number.

66521573 is a deficient number, since it is larger than the sum of its proper divisors (1).

66521573 is an equidigital number, since it uses as much as digits as its factorization.

66521573 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37800, while the sum is 35.

The square root of 66521573 is about 8156.0758333895. The cubic root of 66521573 is about 405.1857563776.

The spelling of 66521573 in words is "sixty-six million, five hundred twenty-one thousand, five hundred seventy-three".