664321021 has 8 divisors (see below), whose sum is σ = 817625984. Its totient is φ = 525616560.

The previous prime is 664321001. The next prime is 664321069. The reversal of 664321021 is 120123466.

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

It is not a de Polignac number, because 664321021 - 2¹³ = 664312829 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664321001) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3650025 + ... + 3650206.

It is an arithmetic number, because the mean of its divisors is an integer number (102203248).

Almost surely, 2^664321021 is an apocalyptic number.

It is an amenable number.

664321021 is a deficient number, since it is larger than the sum of its proper divisors (153304963).

664321021 is a wasteful number, since it uses less digits than its factorization.

664321021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7300251.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 664321021 is about 25774.4257162017. The cubic root of 664321021 is about 872.5547056445.

Adding to 664321021 its reverse (120123466), we get a palindrome (784444487).

The spelling of 664321021 in words is "six hundred sixty-four million, three hundred twenty-one thousand, twenty-one".