66729661 has 4 divisors (see below), whose sum is σ = 66749632. Its totient is φ = 66709692.

The previous prime is 66729659. The next prime is 66729713. The reversal of 66729661 is 16692766.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16692766 = 2 ⋅8346383.

It is a cyclic number.

It is not a de Polignac number, because 66729661 - 2¹ = 66729659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66729161) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3621 + ... + 12106.

It is an arithmetic number, because the mean of its divisors is an integer number (16687408).

Almost surely, 2^66729661 is an apocalyptic number.

It is an amenable number.

66729661 is a deficient number, since it is larger than the sum of its proper divisors (19971).

66729661 is a wasteful number, since it uses less digits than its factorization.

66729661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19970.

The product of its digits is 163296, while the sum is 43.

The square root of 66729661 is about 8168.8224977655. The cubic root of 66729661 is about 405.6078075861.

The spelling of 66729661 in words is "sixty-six million, seven hundred twenty-nine thousand, six hundred sixty-one".