666400026666 has 128 divisors (see below), whose sum is σ = 1548761472000. Its totient is φ = 189034560000.

The previous prime is 666400026659. The next prime is 666400026689. The reversal of 666400026666 is 666620004666.

It is a super-2 number, since 2×666400026666² (a number of 24 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 65981685 + ... + 65991783.

It is an arithmetic number, because the mean of its divisors is an integer number (12099699000).

Almost surely, 2^666400026666 is an apocalyptic number.

666400026666 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 666400026666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (774380736000).

666400026666 is an abundant number, since it is smaller than the sum of its proper divisors (882361445334).

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

666400026666 is a wasteful number, since it uses less digits than its factorization.

666400026666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10756.

The product of its (nonzero) digits is 2239488, while the sum is 48.

The spelling of 666400026666 in words is "six hundred sixty-six billion, four hundred million, twenty-six thousand, six hundred sixty-six".