665623251 has 20 divisors (see below), whose sum is σ = 1000929424. Its totient is φ = 440802000.

The previous prime is 665623241. The next prime is 665623267. The reversal of 665623251 is 152326566.

It is a happy number.

665623251 is a `hidden beast` number, since 6 + 6 + 5 + 623 + 25 + 1 = 666.

It is not a de Polignac number, because 665623251 - 2⁹ = 665622739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665623201) by changing a digit.

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 19 ways as a sum of consecutive naturals, for example, 14980 + ... + 39441.

Almost surely, 2^665623251 is an apocalyptic number.

665623251 is a deficient number, since it is larger than the sum of its proper divisors (335306173).

665623251 is a wasteful number, since it uses less digits than its factorization.

665623251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54584 (or 54575 counting only the distinct ones).

The product of its digits is 64800, while the sum is 36.

The square root of 665623251 is about 25799.6754049348. The cubic root of 665623251 is about 873.1244729875.

The spelling of 665623251 in words is "six hundred sixty-five million, six hundred twenty-three thousand, two hundred fifty-one".