661130221 has 4 divisors (see below), whose sum is σ = 700020252. Its totient is φ = 622240192.

The previous prime is 661130219. The next prime is 661130237. The reversal of 661130221 is 122031166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 122031166 = 2 ⋅61015583.

It can be written as a sum of positive squares in 2 ways, for example, as 580328100 + 80802121 = 24090^2 + 8989^2 .

It is a cyclic number.

It is not a de Polignac number, because 661130221 - 2¹ = 661130219 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 661130192 and 661130201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661130291) 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, 19444990 + ... + 19445023.

It is an arithmetic number, because the mean of its divisors is an integer number (175005063).

Almost surely, 2^661130221 is an apocalyptic number.

It is an amenable number.

661130221 is a deficient number, since it is larger than the sum of its proper divisors (38890031).

661130221 is a wasteful number, since it uses less digits than its factorization.

661130221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38890030.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 661130221 is about 25712.4526445845. The cubic root of 661130221 is about 871.1554739920.

Adding to 661130221 its reverse (122031166), we get a palindrome (783161387).

The spelling of 661130221 in words is "six hundred sixty-one million, one hundred thirty thousand, two hundred twenty-one".