660421821 has 8 divisors (see below), whose sum is σ = 901040800. Its totient is φ = 430042032.

The previous prime is 660421781. The next prime is 660421847. The reversal of 660421821 is 128124066.

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

It is not a de Polignac number, because 660421821 - 2⁶ = 660421757 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 (660421921) 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 7 ways as a sum of consecutive naturals, for example, 2559646 + ... + 2559903.

It is an arithmetic number, because the mean of its divisors is an integer number (112630100).

Almost surely, 2^660421821 is an apocalyptic number.

It is an amenable number.

660421821 is a deficient number, since it is larger than the sum of its proper divisors (240618979).

660421821 is a wasteful number, since it uses less digits than its factorization.

660421821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5119595.

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 660421821 is about 25698.6735260791. The cubic root of 660421821 is about 870.8442155510.

Adding to 660421821 its reverse (128124066), we get a palindrome (788545887).

The spelling of 660421821 in words is "six hundred sixty million, four hundred twenty-one thousand, eight hundred twenty-one".