15661635557 has 2 divisors, whose sum is σ = 15661635558. Its totient is φ = 15661635556.

The previous prime is 15661635499. The next prime is 15661635559. The reversal of 15661635557 is 75553616651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8765827876 + 6895807681 = 93626^2 + 83041^2 .

It is an emirp because it is prime and its reverse (75553616651) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15661635557 - 2¹⁰ = 15661634533 is a prime.

Together with 15661635559, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15661635559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7830817778 + 7830817779.

It is an arithmetic number, because the mean of its divisors is an integer number (7830817779).

Almost surely, 2^15661635557 is an apocalyptic number.

It is an amenable number.

15661635557 is a deficient number, since it is larger than the sum of its proper divisors (1).

15661635557 is an equidigital number, since it uses as much as digits as its factorization.

15661635557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2835000, while the sum is 50.

The spelling of 15661635557 in words is "fifteen billion, six hundred sixty-one million, six hundred thirty-five thousand, five hundred fifty-seven".