1664621280 has 480 divisors, whose sum is σ = 6849722880. Its totient is φ = 372833280.

The previous prime is 1664621261. The next prime is 1664621311. The reversal of 1664621280 is 821264661.

1664621280 is a `hidden beast` number, since 1 + 6 + 6 + 4 + 621 + 28 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (480).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 5352325 + ... + 5352635.

It is an arithmetic number, because the mean of its divisors is an integer number (14270256).

Almost surely, 2^1664621280 is an apocalyptic number.

1664621280 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 1664621280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3424861440).

1664621280 is an abundant number, since it is smaller than the sum of its proper divisors (5185101600).

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

1664621280 is a wasteful number, since it uses less digits than its factorization.

1664621280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404 (or 387 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 1664621280 is about 40799.7705875903. The cubic root of 1664621280 is about 1185.1458881434.

The spelling of 1664621280 in words is "one billion, six hundred sixty-four million, six hundred twenty-one thousand, two hundred eighty".