1666666400 has 432 divisors, whose sum is σ = 5217837912. Its totient is φ = 516096000.

The previous prime is 1666666399. The next prime is 1666666403. The reversal of 1666666400 is 46666661.

It can be written as a sum of positive squares in 12 ways, for example, as 56731024 + 1609935376 = 7532^2 + 40124^2 .

It is a Harshad number since it is a multiple of its sum of digits (41).

It is not an unprimeable number, because it can be changed into a prime (1666666403) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 27322370 + ... + 27322430.

Almost surely, 2^1666666400 is an apocalyptic number.

1666666400 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1666666400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2608918956).

1666666400 is an abundant number, since it is smaller than the sum of its proper divisors (3551171512).

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

1666666400 is a wasteful number, since it uses less digits than its factorization.

1666666400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153 (or 133 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 41.

The square root of 1666666400 is about 40824.8257803998. The cubic root of 1666666400 is about 1185.6310382630.

It can be divided in two parts, 1666 and 666400, that multiplied together give a square (1110222400 = 33320²).

The spelling of 1666666400 in words is "one billion, six hundred sixty-six million, six hundred sixty-six thousand, four hundred".