1561257605 has 4 divisors (see below), whose sum is σ = 1873509132. Its totient is φ = 1249006080.

The previous prime is 1561257589. The next prime is 1561257671. The reversal of 1561257605 is 5067521651.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1109822596 + 451435009 = 33314^2 + 21247^2 .

It is not a de Polignac number, because 1561257605 - 2⁴ = 1561257589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 156125756 + ... + 156125765.

It is an arithmetic number, because the mean of its divisors is an integer number (468377283).

Almost surely, 2^1561257605 is an apocalyptic number.

It is an amenable number.

1561257605 is a deficient number, since it is larger than the sum of its proper divisors (312251527).

1561257605 is an equidigital number, since it uses as much as digits as its factorization.

1561257605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 312251526.

The product of its (nonzero) digits is 63000, while the sum is 38.

The square root of 1561257605 is about 39512.7524351316. The cubic root of 1561257605 is about 1160.0895702239.

The spelling of 1561257605 in words is "one billion, five hundred sixty-one million, two hundred fifty-seven thousand, six hundred five".