1656617561 has 2 divisors, whose sum is σ = 1656617562. Its totient is φ = 1656617560.

The previous prime is 1656617551. The next prime is 1656617579. The reversal of 1656617561 is 1657166561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1209717961 + 446899600 = 34781^2 + 21140^2 .

It is a cyclic number.

It is not a de Polignac number, because 1656617561 - 2⁶ = 1656617497 is a prime.

It is not a weakly prime, because it can be changed into another prime (1656617531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 828308780 + 828308781.

It is an arithmetic number, because the mean of its divisors is an integer number (828308781).

Almost surely, 2^1656617561 is an apocalyptic number.

It is an amenable number.

1656617561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1656617561 is an equidigital number, since it uses as much as digits as its factorization.

1656617561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 226800, while the sum is 44.

The square root of 1656617561 is about 40701.5670582841. The cubic root of 1656617561 is about 1183.2433897296.

The spelling of 1656617561 in words is "one billion, six hundred fifty-six million, six hundred seventeen thousand, five hundred sixty-one".