664623121 has 4 divisors (see below), whose sum is σ = 675518644. Its totient is φ = 653727600.

The previous prime is 664623101. The next prime is 664623137. The reversal of 664623121 is 121326466.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 121326466 = 2 ⋅60663233.

It can be written as a sum of positive squares in 2 ways, for example, as 237622225 + 427000896 = 15415^2 + 20664^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-664623121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664623101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5447670 + ... + 5447791.

It is an arithmetic number, because the mean of its divisors is an integer number (168879661).

Almost surely, 2^664623121 is an apocalyptic number.

664623121 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

664623121 is a deficient number, since it is larger than the sum of its proper divisors (10895523).

664623121 is a wasteful number, since it uses less digits than its factorization.

664623121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10895522.

The product of its digits is 10368, while the sum is 31.

The square root of 664623121 is about 25780.2855104438. The cubic root of 664623121 is about 872.6869503581.

Adding to 664623121 its reverse (121326466), we get a palindrome (785949587).

The spelling of 664623121 in words is "six hundred sixty-four million, six hundred twenty-three thousand, one hundred twenty-one".