661003221 has 16 divisors (see below), whose sum is σ = 891113600. Its totient is φ = 435792960.

The previous prime is 661003219. The next prime is 661003237. The reversal of 661003221 is 122300166.

It is a happy number.

It is not a de Polignac number, because 661003221 - 2¹ = 661003219 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661003621) 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, 425955 + ... + 427503.

It is an arithmetic number, because the mean of its divisors is an integer number (55694600).

Almost surely, 2^661003221 is an apocalyptic number.

It is an amenable number.

661003221 is a deficient number, since it is larger than the sum of its proper divisors (230110379).

661003221 is a wasteful number, since it uses less digits than its factorization.

661003221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3036.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 661003221 is about 25709.9829054786. The cubic root of 661003221 is about 871.0996887994.

Adding to 661003221 its reverse (122300166), we get a palindrome (783303387).

The spelling of 661003221 in words is "six hundred sixty-one million, three thousand, two hundred twenty-one".