1666816651 has 8 divisors (see below), whose sum is σ = 1672598880. Its totient is φ = 1661045568.

The previous prime is 1666816639. The next prime is 1666816681. The reversal of 1666816651 is 1566186661.

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

It is a cyclic number.

It is not a de Polignac number, because 1666816651 - 2⁷ = 1666816523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666816631) 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, 383050 + ... + 387376.

It is an arithmetic number, because the mean of its divisors is an integer number (209074860).

Almost surely, 2^1666816651 is an apocalyptic number.

1666816651 is a deficient number, since it is larger than the sum of its proper divisors (5782229).

1666816651 is an equidigital number, since it uses as much as digits as its factorization.

1666816651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5573.

The product of its digits is 311040, while the sum is 46.

The square root of 1666816651 is about 40826.6659304920. The cubic root of 1666816651 is about 1185.6666656480. Note that the first 5 decimals are identical.

The spelling of 1666816651 in words is "one billion, six hundred sixty-six million, eight hundred sixteen thousand, six hundred fifty-one".