1639840621 has 12 divisors (see below), whose sum is σ = 1743483700. Its totient is φ = 1542044160.

The previous prime is 1639840607. The next prime is 1639840627. The reversal of 1639840621 is 1260489361.

It can be written as a sum of positive squares in 6 ways, for example, as 149108521 + 1490732100 = 12211^2 + 38610^2 .

It is not a de Polignac number, because 1639840621 - 2⁵ = 1639840589 is a prime.

It is a hoax number, since the sum of its digits (40) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1639840627) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 536305 + ... + 539353.

Almost surely, 2^1639840621 is an apocalyptic number.

It is an amenable number.

1639840621 is a deficient number, since it is larger than the sum of its proper divisors (103643079).

1639840621 is a wasteful number, since it uses less digits than its factorization.

1639840621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4944 (or 4927 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 40.

The square root of 1639840621 is about 40494.9456228799. The cubic root of 1639840621 is about 1179.2355052394.

It can be divided in two parts, 1639840 and 621, that added together give a palindrome (1640461).

The spelling of 1639840621 in words is "one billion, six hundred thirty-nine million, eight hundred forty thousand, six hundred twenty-one".