1645256720 has 20 divisors (see below), whose sum is σ = 3825222060. Its totient is φ = 658102656.

The previous prime is 1645256693. The next prime is 1645256737. The reversal of 1645256720 is 276525461.

It can be written as a sum of positive squares in 2 ways, for example, as 944701696 + 700555024 = 30736^2 + 26468^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10282775 + ... + 10282934.

It is an arithmetic number, because the mean of its divisors is an integer number (191261103).

Almost surely, 2^1645256720 is an apocalyptic number.

1645256720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1645256720 is an abundant number, since it is smaller than the sum of its proper divisors (2179965340).

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

1645256720 is a wasteful number, since it uses less digits than its factorization.

1645256720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20565722 (or 20565716 counting only the distinct ones).

The product of its (nonzero) digits is 100800, while the sum is 38.

The square root of 1645256720 is about 40561.7642614322. The cubic root of 1645256720 is about 1180.5323462223.

The spelling of 1645256720 in words is "one billion, six hundred forty-five million, two hundred fifty-six thousand, seven hundred twenty".