661335021 has 12 divisors (see below), whose sum is σ = 958152000. Its totient is φ = 439556040.

The previous prime is 661335019. The next prime is 661335041. The reversal of 661335021 is 120533166.

It is not a de Polignac number, because 661335021 - 2¹ = 661335019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661335001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 108021 + ... + 113978.

It is an arithmetic number, because the mean of its divisors is an integer number (79846000).

Almost surely, 2^661335021 is an apocalyptic number.

It is an amenable number.

661335021 is a deficient number, since it is larger than the sum of its proper divisors (296816979).

661335021 is a wasteful number, since it uses less digits than its factorization.

661335021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222336 (or 222333 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 27.

The square root of 661335021 is about 25716.4348423338. The cubic root of 661335021 is about 871.2454180586.

Adding to 661335021 its reverse (120533166), we get a palindrome (781868187).

The spelling of 661335021 in words is "six hundred sixty-one million, three hundred thirty-five thousand, twenty-one".