644689963 has 8 divisors (see below), whose sum is σ = 686387520. Its totient is φ = 603411840.

The previous prime is 644689957. The next prime is 644689987. The reversal of 644689963 is 369986446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644689963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644689943) 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, 101683 + ... + 107836.

It is an arithmetic number, because the mean of its divisors is an integer number (85798440).

Almost surely, 2^644689963 is an apocalyptic number.

644689963 is a deficient number, since it is larger than the sum of its proper divisors (41697557).

644689963 is a wasteful number, since it uses less digits than its factorization.

644689963 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209717.

The product of its digits is 6718464, while the sum is 55.

The square root of 644689963 is about 25390.7456172520. The cubic root of 644689963 is about 863.8738004941.

The spelling of 644689963 in words is "six hundred forty-four million, six hundred eighty-nine thousand, nine hundred sixty-three".