1561252156561 has 4 divisors (see below), whose sum is σ = 1561780144692. Its totient is φ = 1560724168432.

The previous prime is 1561252156549. The next prime is 1561252156571. The reversal of 1561252156561 is 1656512521651.

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 468978432400 + 1092273724161 = 684820^2 + 1045119^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561252156561 - 2⁷ = 1561252156433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561252156501) 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, 263989630 + ... + 263995543.

It is an arithmetic number, because the mean of its divisors is an integer number (390445036173).

Almost surely, 2^{1561252156561} is an apocalyptic number.

It is an amenable number.

1561252156561 is a deficient number, since it is larger than the sum of its proper divisors (527988131).

1561252156561 is an equidigital number, since it uses as much as digits as its factorization.

1561252156561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 527988130.

The product of its digits is 540000, while the sum is 46.

The spelling of 1561252156561 in words is "one trillion, five hundred sixty-one billion, two hundred fifty-two million, one hundred fifty-six thousand, five hundred sixty-one".