66581556 has 48 divisors (see below), whose sum is σ = 158054400. Its totient is φ = 21812832.

The previous prime is 66581551. The next prime is 66581579. The reversal of 66581556 is 65518566.

It is a super-2 number, since 2×66581556² = 8866207198762272, which contains 22 as substring.

It is a hoax number, since the sum of its digits (42) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66581551) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 298461 + ... + 298683.

It is an arithmetic number, because the mean of its divisors is an integer number (3292800).

Almost surely, 2^66581556 is an apocalyptic number.

It is an amenable number.

66581556 is an abundant number, since it is smaller than the sum of its proper divisors (91472844).

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

66581556 is a wasteful number, since it uses less digits than its factorization.

66581556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 548 (or 546 counting only the distinct ones).

The product of its digits is 216000, while the sum is 42.

The square root of 66581556 is about 8159.7522021199. The cubic root of 66581556 is about 405.3075061332.

The spelling of 66581556 in words is "sixty-six million, five hundred eighty-one thousand, five hundred fifty-six".