1644806138 has 4 divisors (see below), whose sum is σ = 2467209210. Its totient is φ = 822403068.

The previous prime is 1644806101. The next prime is 1644806173. The reversal of 1644806138 is 8316084461.

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., 911858809 + 732947329 = 30197^2 + 27073^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1644806095 and 1644806104.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 411201533 + ... + 411201536.

Almost surely, 2^1644806138 is an apocalyptic number.

1644806138 is a deficient number, since it is larger than the sum of its proper divisors (822403072).

1644806138 is an equidigital number, since it uses as much as digits as its factorization.

1644806138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 822403071.

The product of its (nonzero) digits is 110592, while the sum is 41.

The square root of 1644806138 is about 40556.2096108598. The cubic root of 1644806138 is about 1180.4245666509.

The spelling of 1644806138 in words is "one billion, six hundred forty-four million, eight hundred six thousand, one hundred thirty-eight".