56656321721 has 2 divisors, whose sum is σ = 56656321722. Its totient is φ = 56656321720.

The previous prime is 56656321717. The next prime is 56656321723. The reversal of 56656321721 is 12712365665.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 49724094121 + 6932227600 = 222989^2 + 83260^2 .

It is a cyclic number.

It is not a de Polignac number, because 56656321721 - 2² = 56656321717 is a prime.

Together with 56656321723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (56656321723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 28328160860 + 28328160861.

It is an arithmetic number, because the mean of its divisors is an integer number (28328160861).

Almost surely, 2^56656321721 is an apocalyptic number.

It is an amenable number.

56656321721 is a deficient number, since it is larger than the sum of its proper divisors (1).

56656321721 is an equidigital number, since it uses as much as digits as its factorization.

56656321721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 453600, while the sum is 44.

The spelling of 56656321721 in words is "fifty-six billion, six hundred fifty-six million, three hundred twenty-one thousand, seven hundred twenty-one".