661140221 has 16 divisors (see below), whose sum is σ = 792562944. Its totient is φ = 539218944.

The previous prime is 661140199. The next prime is 661140239. The reversal of 661140221 is 122041166.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661140221 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661140281) 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 15 ways as a sum of consecutive naturals, for example, 20435 + ... + 41711.

It is an arithmetic number, because the mean of its divisors is an integer number (49535184).

Almost surely, 2^661140221 is an apocalyptic number.

It is an amenable number.

661140221 is a deficient number, since it is larger than the sum of its proper divisors (131422723).

661140221 is a wasteful number, since it uses less digits than its factorization.

661140221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21500.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 661140221 is about 25712.6471021558. The cubic root of 661140221 is about 871.1598662235.

Adding to 661140221 its reverse (122041166), we get a palindrome (783181387).

The spelling of 661140221 in words is "six hundred sixty-one million, one hundred forty thousand, two hundred twenty-one".