661306921 has 8 divisors (see below), whose sum is σ = 722937600. Its totient is φ = 599928240.

The previous prime is 661306903. The next prime is 661306931. The reversal of 661306921 is 129603166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661306921 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661306901) 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 7 ways as a sum of consecutive naturals, for example, 57486 + ... + 68023.

It is an arithmetic number, because the mean of its divisors is an integer number (90367200).

Almost surely, 2^661306921 is an apocalyptic number.

It is an amenable number.

661306921 is a deficient number, since it is larger than the sum of its proper divisors (61630679).

661306921 is a wasteful number, since it uses less digits than its factorization.

661306921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125999.

The product of its (nonzero) digits is 11664, while the sum is 34.

The square root of 661306921 is about 25715.8884933031. Note that the first 3 decimals coincide. The cubic root of 661306921 is about 871.2330781995.

The spelling of 661306921 in words is "six hundred sixty-one million, three hundred six thousand, nine hundred twenty-one".