1561065551 has 4 divisors (see below), whose sum is σ = 1590519672. Its totient is φ = 1531611432.

The previous prime is 1561065547. The next prime is 1561065559. The reversal of 1561065551 is 1555601651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1555601651 = 739 ⋅2105009.

It is a cyclic number.

It is not a de Polignac number, because 1561065551 - 2² = 1561065547 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561065559) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14726981 + ... + 14727086.

It is an arithmetic number, because the mean of its divisors is an integer number (397629918).

Almost surely, 2^1561065551 is an apocalyptic number.

1561065551 is a deficient number, since it is larger than the sum of its proper divisors (29454121).

1561065551 is an equidigital number, since it uses as much as digits as its factorization.

1561065551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29454120.

The product of its (nonzero) digits is 22500, while the sum is 35.

The square root of 1561065551 is about 39510.3220817042. The cubic root of 1561065551 is about 1160.0419998170.

The spelling of 1561065551 in words is "one billion, five hundred sixty-one million, sixty-five thousand, five hundred fifty-one".