644529986 has 4 divisors (see below), whose sum is σ = 966794982. Its totient is φ = 322264992.

The previous prime is 644529929. The next prime is 644530001. The reversal of 644529986 is 689925446.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 641051761 + 3478225 = 25319^2 + 1865^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161132495 + ... + 161132498.

Almost surely, 2^644529986 is an apocalyptic number.

644529986 is a deficient number, since it is larger than the sum of its proper divisors (322264996).

644529986 is a wasteful number, since it uses less digits than its factorization.

644529986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322264995.

The product of its digits is 3732480, while the sum is 53.

The square root of 644529986 is about 25387.5951204520. The cubic root of 644529986 is about 863.8023390787.

The spelling of 644529986 in words is "six hundred forty-four million, five hundred twenty-nine thousand, nine hundred eighty-six".