66561387 has 8 divisors (see below), whose sum is σ = 88796736. Its totient is φ = 44350152.

The previous prime is 66561373. The next prime is 66561403. The reversal of 66561387 is 78316566.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 66561387 - 2¹⁵ = 66528619 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66561337) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1908 + ... + 11694.

It is an arithmetic number, because the mean of its divisors is an integer number (11099592).

Almost surely, 2^66561387 is an apocalyptic number.

66561387 is a deficient number, since it is larger than the sum of its proper divisors (22235349).

66561387 is a wasteful number, since it uses less digits than its factorization.

66561387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12057.

The product of its digits is 181440, while the sum is 42.

The square root of 66561387 is about 8158.5162253929. The cubic root of 66561387 is about 405.2665765167.

The spelling of 66561387 in words is "sixty-six million, five hundred sixty-one thousand, three hundred eighty-seven".