1556727661 has 2 divisors, whose sum is σ = 1556727662. Its totient is φ = 1556727660.

The previous prime is 1556727659. The next prime is 1556727671. The reversal of 1556727661 is 1667276551.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1544018436 + 12709225 = 39294^2 + 3565^2 .

It is a cyclic number.

It is not a de Polignac number, because 1556727661 - 2¹ = 1556727659 is a prime.

Together with 1556727659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1556727631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 778363830 + 778363831.

It is an arithmetic number, because the mean of its divisors is an integer number (778363831).

Almost surely, 2^1556727661 is an apocalyptic number.

It is an amenable number.

1556727661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1556727661 is an equidigital number, since it uses as much as digits as its factorization.

1556727661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 529200, while the sum is 46.

The square root of 1556727661 is about 39455.3882378567. The cubic root of 1556727661 is about 1158.9664945003.

The spelling of 1556727661 in words is "one billion, five hundred fifty-six million, seven hundred twenty-seven thousand, six hundred sixty-one".