664819 has 4 divisors (see below), whose sum is σ = 703944. Its totient is φ = 625696.

The previous prime is 664799. The next prime is 664843. The reversal of 664819 is 918466.

664819 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 918466 = 2 ⋅459233.

It is a cyclic number.

It is not a de Polignac number, because 664819 - 2⁷ = 664691 is a prime.

It is a super-2 number, since 2×664819² = 883968605522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664849) 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, 19537 + ... + 19570.

It is an arithmetic number, because the mean of its divisors is an integer number (175986).

2⁶⁶⁴⁸¹⁹ is an apocalyptic number.

664819 is a deficient number, since it is larger than the sum of its proper divisors (39125).

664819 is a wasteful number, since it uses less digits than its factorization.

664819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39124.

The product of its digits is 10368, while the sum is 34.

The square root of 664819 is about 815.3643357420. The cubic root of 664819 is about 87.2772675261.

The spelling of 664819 in words is "six hundred sixty-four thousand, eight hundred nineteen".