644666505 has 16 divisors (see below), whose sum is σ = 1178818944. Its totient is φ = 294704640.

The previous prime is 644666489. The next prime is 644666527. The reversal of 644666505 is 505666446.

It is a happy number.

It is not a de Polignac number, because 644666505 - 2⁴ = 644666489 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3069736 + ... + 3069945.

It is an arithmetic number, because the mean of its divisors is an integer number (73676184).

Almost surely, 2^644666505 is an apocalyptic number.

It is an amenable number.

644666505 is a deficient number, since it is larger than the sum of its proper divisors (534152439).

644666505 is a wasteful number, since it uses less digits than its factorization.

644666505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6139696.

The product of its (nonzero) digits is 518400, while the sum is 42.

The square root of 644666505 is about 25390.2836730904. The cubic root of 644666505 is about 863.8633225908.

The spelling of 644666505 in words is "six hundred forty-four million, six hundred sixty-six thousand, five hundred five".