664999969 has 4 divisors (see below), whose sum is σ = 665054596. Its totient is φ = 664945344.

The previous prime is 664999949. The next prime is 665000027. The reversal of 664999969 is 969999466.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 969999466 = 2 ⋅484999733.

It can be written as a sum of positive squares in 2 ways, for example, as 121550625 + 543449344 = 11025^2 + 23312^2 .

It is a cyclic number.

It is not a de Polignac number, because 664999969 - 2¹⁵ = 664967201 is a prime.

It is a super-2 number, since 2×664999969² = 884449917540001922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664999939) 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, 157 + ... + 36469.

It is an arithmetic number, because the mean of its divisors is an integer number (166263649).

Almost surely, 2^664999969 is an apocalyptic number.

It is an amenable number.

664999969 is a deficient number, since it is larger than the sum of its proper divisors (54627).

664999969 is a wasteful number, since it uses less digits than its factorization.

664999969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54626.

The product of its digits is 51018336, while the sum is 67.

The square root of 664999969 is about 25787.5933153910. The cubic root of 664999969 is about 872.8518599555.

The spelling of 664999969 in words is "six hundred sixty-four million, nine hundred ninety-nine thousand, nine hundred sixty-nine".