1561656551 has 16 divisors (see below), whose sum is σ = 1925652288. Its totient is φ = 1233273600.

The previous prime is 1561656539. The next prime is 1561656559. The reversal of 1561656551 is 1556561651.

It is not a de Polignac number, because 1561656551 - 2⁶ = 1561656487 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1561656499 and 1561656508.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561656559) 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 in 15 ways as a sum of consecutive naturals, for example, 33371 + ... + 65091.

It is an arithmetic number, because the mean of its divisors is an integer number (120353268).

Almost surely, 2^1561656551 is an apocalyptic number.

1561656551 is a deficient number, since it is larger than the sum of its proper divisors (363995737).

1561656551 is a wasteful number, since it uses less digits than its factorization.

1561656551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32282.

The product of its digits is 135000, while the sum is 41.

The square root of 1561656551 is about 39517.8004322103. The cubic root of 1561656551 is about 1160.1883738373.

The spelling of 1561656551 in words is "one billion, five hundred sixty-one million, six hundred fifty-six thousand, five hundred fifty-one".