665520638 has 16 divisors (see below), whose sum is σ = 1052862720. Its totient is φ = 314634456.

The previous prime is 665520637. The next prime is 665520659. The reversal of 665520638 is 836025566.

It is a junction number, because it is equal to n+sod(n) for n = 665520595 and 665520604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665520631) 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, 3131 + ... + 36617.

It is an arithmetic number, because the mean of its divisors is an integer number (65803920).

Almost surely, 2^665520638 is an apocalyptic number.

665520638 is a deficient number, since it is larger than the sum of its proper divisors (387342082).

665520638 is a wasteful number, since it uses less digits than its factorization.

665520638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34031.

The product of its (nonzero) digits is 259200, while the sum is 41.

The square root of 665520638 is about 25797.6866792354. The cubic root of 665520638 is about 873.0796034983.

The spelling of 665520638 in words is "six hundred sixty-five million, five hundred twenty thousand, six hundred thirty-eight".