16556221757 has 2 divisors, whose sum is σ = 16556221758. Its totient is φ = 16556221756.

The previous prime is 16556221697. The next prime is 16556221831. The reversal of 16556221757 is 75712265561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15717887641 + 838334116 = 125371^2 + 28954^2 .

It is a cyclic number.

It is not a de Polignac number, because 16556221757 - 2³² = 12261254461 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16556721757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8278110878 + 8278110879.

It is an arithmetic number, because the mean of its divisors is an integer number (8278110879).

Almost surely, 2^16556221757 is an apocalyptic number.

It is an amenable number.

16556221757 is a deficient number, since it is larger than the sum of its proper divisors (1).

16556221757 is an equidigital number, since it uses as much as digits as its factorization.

16556221757 is an evil number, because the sum of its binary digits is even.

The product of its digits is 882000, while the sum is 47.

The spelling of 16556221757 in words is "sixteen billion, five hundred fifty-six million, two hundred twenty-one thousand, seven hundred fifty-seven".