66451661 has 4 divisors (see below), whose sum is σ = 66468000. Its totient is φ = 66435324.

The previous prime is 66451633. The next prime is 66451687. The reversal of 66451661 is 16615466.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66451661 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 (66451261) 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, 3290 + ... + 11988.

It is an arithmetic number, because the mean of its divisors is an integer number (16617000).

Almost surely, 2^66451661 is an apocalyptic number.

It is an amenable number.

66451661 is a deficient number, since it is larger than the sum of its proper divisors (16339).

66451661 is an equidigital number, since it uses as much as digits as its factorization.

66451661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16338.

The product of its digits is 25920, while the sum is 35.

The square root of 66451661 is about 8151.7888220930. The cubic root of 66451661 is about 405.0437609575.

It can be divided in two parts, 664 and 51661, that added together give a palindrome (52325).

The spelling of 66451661 in words is "sixty-six million, four hundred fifty-one thousand, six hundred sixty-one".