644503028402 has 4 divisors (see below), whose sum is σ = 966754542606. Its totient is φ = 322251514200.

The previous prime is 644503028333. The next prime is 644503028413. The reversal of 644503028402 is 204820305446.

It is a happy number.

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., 603447758761 + 41055269641 = 776819^2 + 202621^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161125757099 + ... + 161125757102.

Almost surely, 2^644503028402 is an apocalyptic number.

644503028402 is a deficient number, since it is larger than the sum of its proper divisors (322251514204).

644503028402 is a wasteful number, since it uses less digits than its factorization.

644503028402 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322251514203.

The product of its (nonzero) digits is 184320, while the sum is 38.

The spelling of 644503028402 in words is "six hundred forty-four billion, five hundred three million, twenty-eight thousand, four hundred two".