1561000121 has 4 divisors (see below), whose sum is σ = 1561442532. Its totient is φ = 1560557712.

The previous prime is 1561000117. The next prime is 1561000153. The reversal of 1561000121 is 1210001651.

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 89510521 + 1471489600 = 9461^2 + 38360^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561000121 - 2² = 1561000117 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1561000121.

It is not an unprimeable number, because it can be changed into a prime (1561000171) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 215870 + ... + 222983.

It is an arithmetic number, because the mean of its divisors is an integer number (390360633).

Almost surely, 2^1561000121 is an apocalyptic number.

It is an amenable number.

1561000121 is a deficient number, since it is larger than the sum of its proper divisors (442411).

1561000121 is an equidigital number, since it uses as much as digits as its factorization.

1561000121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 442410.

The product of its (nonzero) digits is 60, while the sum is 17.

The square root of 1561000121 is about 39509.4940615544. The cubic root of 1561000121 is about 1160.0257923813.

Adding to 1561000121 its reverse (1210001651), we get a palindrome (2771001772).

The spelling of 1561000121 in words is "one billion, five hundred sixty-one million, one hundred twenty-one", and thus it is an aban number.