1561786997 has 2 divisors, whose sum is σ = 1561786998. Its totient is φ = 1561786996.

The previous prime is 1561786981. The next prime is 1561786999. The reversal of 1561786997 is 7996871651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1560724036 + 1062961 = 39506^2 + 1031^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561786997 - 2⁴ = 1561786981 is a prime.

Together with 1561786999, 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 (1561786999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780893498 + 780893499.

It is an arithmetic number, because the mean of its divisors is an integer number (780893499).

Almost surely, 2^1561786997 is an apocalyptic number.

It is an amenable number.

1561786997 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561786997 is an equidigital number, since it uses as much as digits as its factorization.

1561786997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5715360, while the sum is 59.

The square root of 1561786997 is about 39519.4508691606. The cubic root of 1561786997 is about 1160.2206766547.

The spelling of 1561786997 in words is "one billion, five hundred sixty-one million, seven hundred eighty-six thousand, nine hundred ninety-seven".