665621615 has 16 divisors (see below), whose sum is σ = 825335040. Its totient is φ = 514805760.

The previous prime is 665621603. The next prime is 665621651. The reversal of 665621615 is 516126566.

It is not a de Polignac number, because 665621615 - 2¹⁴ = 665605231 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 246191 + ... + 248879.

It is an arithmetic number, because the mean of its divisors is an integer number (51583440).

Almost surely, 2^665621615 is an apocalyptic number.

665621615 is a deficient number, since it is larger than the sum of its proper divisors (159713425).

665621615 is a wasteful number, since it uses less digits than its factorization.

665621615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4322.

The product of its digits is 64800, while the sum is 38.

The square root of 665621615 is about 25799.6436990901. The cubic root of 665621615 is about 873.1237576515.

The spelling of 665621615 in words is "six hundred sixty-five million, six hundred twenty-one thousand, six hundred fifteen".