66121665 has 16 divisors (see below), whose sum is σ = 110395008. Its totient is φ = 33731456.

The previous prime is 66121663. The next prime is 66121669. The reversal of 66121665 is 56612166.

It is a cyclic number.

It is not a de Polignac number, because 66121665 - 2¹ = 66121663 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66121663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 95484 + ... + 96173.

It is an arithmetic number, because the mean of its divisors is an integer number (6899688).

Almost surely, 2^66121665 is an apocalyptic number.

It is an amenable number.

66121665 is a deficient number, since it is larger than the sum of its proper divisors (44273343).

66121665 is a wasteful number, since it uses less digits than its factorization.

66121665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191688.

The product of its digits is 12960, while the sum is 33.

The square root of 66121665 is about 8131.5229200931. The cubic root of 66121665 is about 404.3721715851.

The spelling of 66121665 in words is "sixty-six million, one hundred twenty-one thousand, six hundred sixty-five".