1656128720 has 20 divisors (see below), whose sum is σ = 3850499460. Its totient is φ = 662451456.

The previous prime is 1656128659. The next prime is 1656128741. The reversal of 1656128720 is 278216561.

It can be written as a sum of positive squares in 2 ways, for example, as 689167504 + 966961216 = 26252^2 + 31096^2 .

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

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors.

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 3 ways as a sum of consecutive naturals, for example, 10350725 + ... + 10350884.

It is an arithmetic number, because the mean of its divisors is an integer number (192524973).

Almost surely, 2^1656128720 is an apocalyptic number.

1656128720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1656128720 is an abundant number, since it is smaller than the sum of its proper divisors (2194370740).

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

1656128720 is a wasteful number, since it uses less digits than its factorization.

1656128720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20701622 (or 20701616 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 38.

The square root of 1656128720 is about 40695.5614287357. The cubic root of 1656128720 is about 1183.1269929625.

The spelling of 1656128720 in words is "one billion, six hundred fifty-six million, one hundred twenty-eight thousand, seven hundred twenty".