1561866623 has 2 divisors, whose sum is σ = 1561866624. Its totient is φ = 1561866622.

The previous prime is 1561866599. The next prime is 1561866643. The reversal of 1561866623 is 3266681651.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1561866623 - 2¹⁴ = 1561850239 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1561866643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780933311 + 780933312.

It is an arithmetic number, because the mean of its divisors is an integer number (780933312).

Almost surely, 2^1561866623 is an apocalyptic number.

1561866623 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561866623 is an equidigital number, since it uses as much as digits as its factorization.

1561866623 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 311040, while the sum is 44.

The square root of 1561866623 is about 39520.4582842861. The cubic root of 1561866623 is about 1160.2403938465.

The spelling of 1561866623 in words is "one billion, five hundred sixty-one million, eight hundred sixty-six thousand, six hundred twenty-three".