1645621920 has 480 divisors, whose sum is σ = 6300866880. Its totient is φ = 403107840.

The previous prime is 1645621919. The next prime is 1645622003. The reversal of 1645621920 is 291265461.

1645621920 is a `hidden beast` number, since 1 + 6 + 4 + 5 + 621 + 9 + 20 = 666.

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

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 10095759 + ... + 10095921.

It is an arithmetic number, because the mean of its divisors is an integer number (13126806).

Almost surely, 2^1645621920 is an apocalyptic number.

1645621920 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 1645621920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3150433440).

1645621920 is an abundant number, since it is smaller than the sum of its proper divisors (4655244960).

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

1645621920 is a wasteful number, since it uses less digits than its factorization.

1645621920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 250 (or 233 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 1645621920 is about 40566.2657882137. The cubic root of 1645621920 is about 1180.6196879143.

The spelling of 1645621920 in words is "one billion, six hundred forty-five million, six hundred twenty-one thousand, nine hundred twenty".