15664937821 has 4 divisors (see below), whose sum is σ = 16869933052. Its totient is φ = 14459942592.

The previous prime is 15664937779. The next prime is 15664937851. The reversal of 15664937821 is 12873946651.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1344028921 + 14320908900 = 36661^2 + 119670^2 .

It is a cyclic number.

It is not a de Polignac number, because 15664937821 - 2¹¹ = 15664935773 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15664937851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 602497596 + ... + 602497621.

It is an arithmetic number, because the mean of its divisors is an integer number (4217483263).

Almost surely, 2^15664937821 is an apocalyptic number.

It is an amenable number.

15664937821 is a deficient number, since it is larger than the sum of its proper divisors (1204995231).

15664937821 is a wasteful number, since it uses less digits than its factorization.

15664937821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1204995230.

The product of its digits is 2177280, while the sum is 52.

The spelling of 15664937821 in words is "fifteen billion, six hundred sixty-four million, nine hundred thirty-seven thousand, eight hundred twenty-one".