121331561 has 4 divisors (see below), whose sum is σ = 130664772. Its totient is φ = 111998352.

The previous prime is 121331531. The next prime is 121331627. The reversal of 121331561 is 165133121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165133121 = 17 ⋅9713713.

It can be written as a sum of positive squares in 2 ways, for example, as 64705936 + 56625625 = 8044^2 + 7525^2 .

It is a cyclic number.

It is not a de Polignac number, because 121331561 - 2¹⁰ = 121330537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121331531) 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, 4666586 + ... + 4666611.

It is an arithmetic number, because the mean of its divisors is an integer number (32666193).

Almost surely, 2^121331561 is an apocalyptic number.

It is an amenable number.

121331561 is a deficient number, since it is larger than the sum of its proper divisors (9333211).

121331561 is an equidigital number, since it uses as much as digits as its factorization.

121331561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9333210.

The product of its digits is 540, while the sum is 23.

The square root of 121331561 is about 11015.0606444086. The cubic root of 121331561 is about 495.0601035749.

Adding to 121331561 its reverse (165133121), we get a palindrome (286464682).

The spelling of 121331561 in words is "one hundred twenty-one million, three hundred thirty-one thousand, five hundred sixty-one".