1666738944 has 288 divisors, whose sum is σ = 5396977600. Its totient is φ = 510603264.

The previous prime is 1666738903. The next prime is 1666738949. The reversal of 1666738944 is 4498376661.

It is a tau number, because it is divible by the number of its divisors (288).

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nialpdrome in base 6.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666738949) 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, 7278222 + ... + 7278450.

Almost surely, 2^1666738944 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1666738944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2698488800).

1666738944 is an abundant number, since it is smaller than the sum of its proper divisors (3730238656).

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

1666738944 is an frugal number, since it uses more digits than its factorization.

1666738944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279 (or 247 counting only the distinct ones).

The product of its digits is 5225472, while the sum is 54.

The square root of 1666738944 is about 40825.7142497226. The cubic root of 1666738944 is about 1185.6482400998.

It can be divided in two parts, 16667 and 38944, that added together give a triangular number (55611 = T₃₃₃).

The spelling of 1666738944 in words is "one billion, six hundred sixty-six million, seven hundred thirty-eight thousand, nine hundred forty-four".