664721451 has 16 divisors (see below), whose sum is σ = 986419200. Its totient is φ = 442406664.

The previous prime is 664721419. The next prime is 664721461. The reversal of 664721451 is 154127466.

664721451 is a `hidden beast` number, since 6 + 647 + 2 + 1 + 4 + 5 + 1 = 666.

It is not a de Polignac number, because 664721451 - 2⁵ = 664721419 is a prime.

It is not an unprimeable number, because it can be changed into a prime (664721461) 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 15 ways as a sum of consecutive naturals, for example, 3891 + ... + 36668.

It is an arithmetic number, because the mean of its divisors is an integer number (61651200).

Almost surely, 2^664721451 is an apocalyptic number.

664721451 is a deficient number, since it is larger than the sum of its proper divisors (321697749).

664721451 is a wasteful number, since it uses less digits than its factorization.

664721451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41175 (or 41169 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 664721451 is about 25782.1925173171. The cubic root of 664721451 is about 872.7299858137.

The spelling of 664721451 in words is "six hundred sixty-four million, seven hundred twenty-one thousand, four hundred fifty-one".