1561121563 has 2 divisors, whose sum is σ = 1561121564. Its totient is φ = 1561121562.

The previous prime is 1561121557. The next prime is 1561121581. The reversal of 1561121563 is 3651211651.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1561121563 is a prime.

It is not a weakly prime, because it can be changed into another prime (1561121593) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780560781 + 780560782.

It is an arithmetic number, because the mean of its divisors is an integer number (780560782).

Almost surely, 2^1561121563 is an apocalyptic number.

1561121563 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561121563 is an equidigital number, since it uses as much as digits as its factorization.

1561121563 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5400, while the sum is 31.

The square root of 1561121563 is about 39511.0309027745. The cubic root of 1561121563 is about 1160.0558739932.

The spelling of 1561121563 in words is "one billion, five hundred sixty-one million, one hundred twenty-one thousand, five hundred sixty-three".