66213661 has 4 divisors (see below), whose sum is σ = 66304000. Its totient is φ = 66123324.

The previous prime is 66213659. The next prime is 66213671. The reversal of 66213661 is 16631266.

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.

It is a cyclic number.

It is not a de Polignac number, because 66213661 - 2¹ = 66213659 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 (66213611) 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, 44061 + ... + 45538.

It is an arithmetic number, because the mean of its divisors is an integer number (16576000).

Almost surely, 2^66213661 is an apocalyptic number.

It is an amenable number.

66213661 is a deficient number, since it is larger than the sum of its proper divisors (90339).

66213661 is an equidigital number, since it uses as much as digits as its factorization.

66213661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90338.

The product of its digits is 7776, while the sum is 31.

The square root of 66213661 is about 8137.1777048311. The cubic root of 66213661 is about 404.5596209031.

The spelling of 66213661 in words is "sixty-six million, two hundred thirteen thousand, six hundred sixty-one".