66521565 has 72 divisors (see below), whose sum is σ = 133617120. Its totient is φ = 30507840.

The previous prime is 66521551. The next prime is 66521573. The reversal of 66521565 is 56512566.

It is a happy number.

It is not a de Polignac number, because 66521565 - 2⁴ = 66521549 is a prime.

It is a super-2 number, since 2×66521565² = 8850237220098450, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 103134 + ... + 103776.

Almost surely, 2^66521565 is an apocalyptic number.

It is an amenable number.

66521565 is an abundant number, since it is smaller than the sum of its proper divisors (67095555).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66521565 is a wasteful number, since it uses less digits than its factorization.

66521565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 695 (or 681 counting only the distinct ones).

The product of its digits is 54000, while the sum is 36.

The square root of 66521565 is about 8156.0753429575. The cubic root of 66521565 is about 405.1857401348.

The spelling of 66521565 in words is "sixty-six million, five hundred twenty-one thousand, five hundred sixty-five".