16639440915721 has 16 divisors (see below), whose sum is σ = 18142599056400. Its totient is φ = 15168585028608.

The previous prime is 16639440915719. The next prime is 16639440915733. The reversal of 16639440915721 is 12751904493661.

It is a happy number.

16639440915721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 8 ways, for example, as 1081622880121 + 15557818035600 = 1040011^2 + 3944340^2 .

It is a cyclic number.

It is not a de Polignac number, because 16639440915721 - 2¹ = 16639440915719 is a prime.

It is a super-2 number, since 2×16639440915721² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (16639440915821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7714876 + ... + 9633181.

It is an arithmetic number, because the mean of its divisors is an integer number (1133912441025).

Almost surely, 2^{16639440915721} is an apocalyptic number.

It is an amenable number.

16639440915721 is a deficient number, since it is larger than the sum of its proper divisors (1503158140679).

16639440915721 is a wasteful number, since it uses less digits than its factorization.

16639440915721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17348988.

The product of its (nonzero) digits is 9797760, while the sum is 58.

The spelling of 16639440915721 in words is "sixteen trillion, six hundred thirty-nine billion, four hundred forty million, nine hundred fifteen thousand, seven hundred twenty-one".