121631561 has 4 divisors (see below), whose sum is σ = 121654224. Its totient is φ = 121608900.

The previous prime is 121631527. The next prime is 121631579. The reversal of 121631561 is 165136121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-121631561 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 121631561.

It is not an unprimeable number, because it can be changed into a prime (121631581) 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, 1766 + ... + 15696.

It is an arithmetic number, because the mean of its divisors is an integer number (30413556).

Almost surely, 2^121631561 is an apocalyptic number.

It is an amenable number.

121631561 is a deficient number, since it is larger than the sum of its proper divisors (22663).

121631561 is an equidigital number, since it uses as much as digits as its factorization.

121631561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22662.

The product of its digits is 1080, while the sum is 26.

The square root of 121631561 is about 11028.6699560736. The cubic root of 121631561 is about 495.4677902778.

Adding to 121631561 its reverse (165136121), we get a palindrome (286767682).

The spelling of 121631561 in words is "one hundred twenty-one million, six hundred thirty-one thousand, five hundred sixty-one".