1561541551 has 2 divisors, whose sum is σ = 1561541552. Its totient is φ = 1561541550.

The previous prime is 1561541549. The next prime is 1561541557. The reversal of 1561541551 is 1551451651.

It is a weak prime.

It is an emirp because it is prime and its reverse (1551451651) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1561541551 - 2¹ = 1561541549 is a prime.

Together with 1561541549, 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 (1561541557) 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, 780770775 + 780770776.

It is an arithmetic number, because the mean of its divisors is an integer number (780770776).

Almost surely, 2^1561541551 is an apocalyptic number.

1561541551 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561541551 is an equidigital number, since it uses as much as digits as its factorization.

1561541551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15000, while the sum is 34.

The square root of 1561541551 is about 39516.3453649246. The cubic root of 1561541551 is about 1160.1598944772.

The spelling of 1561541551 in words is "one billion, five hundred sixty-one million, five hundred forty-one thousand, five hundred fifty-one".