666519915666 has 64 divisors (see below), whose sum is σ = 1475257245696. Its totient is φ = 199056748800.

The previous prime is 666519915653. The next prime is 666519915667.

666519915666 is nontrivially palindromic in base 10.

It is a Harshad number since it is a multiple of its sum of digits (66).

It is a junction number, because it is equal to n+sod(n) for n = 666519915597 and 666519915606.

It is not an unprimeable number, because it can be changed into a prime (666519915667) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 13250335 + ... + 13300541.

It is an arithmetic number, because the mean of its divisors is an integer number (23050894464).

Almost surely, 2^666519915666 is an apocalyptic number.

666519915666 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 666519915666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (737628622848).

666519915666 is an abundant number, since it is smaller than the sum of its proper divisors (808737330030).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

666519915666 is a wasteful number, since it uses less digits than its factorization.

666519915666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53127.

The product of its digits is 94478400, while the sum is 66.

The spelling of 666519915666 in words is "six hundred sixty-six billion, five hundred nineteen million, nine hundred fifteen thousand, six hundred sixty-six".