15643921906 has 4 divisors (see below), whose sum is σ = 23465882862. Its totient is φ = 7821960952.

The previous prime is 15643921897. The next prime is 15643921913. The reversal of 15643921906 is 60912934651.

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., 14271886225 + 1372035681 = 119465^2 + 37041^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3910980475 + ... + 3910980478.

Almost surely, 2^15643921906 is an apocalyptic number.

15643921906 is a deficient number, since it is larger than the sum of its proper divisors (7821960956).

15643921906 is an equidigital number, since it uses as much as digits as its factorization.

15643921906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7821960955.

The product of its (nonzero) digits is 349920, while the sum is 46.

The spelling of 15643921906 in words is "fifteen billion, six hundred forty-three million, nine hundred twenty-one thousand, nine hundred six".