15721721442 has 36 divisors (see below), whose sum is σ = 39625157286. Its totient is φ = 4491920160.

The previous prime is 15721721419. The next prime is 15721721443. The reversal of 15721721442 is 24412712751.

15721721442 is a `hidden beast` number, since 1 + 572 + 1 + 72 + 14 + 4 + 2 = 666.

15721721442 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 only one way, i.e., 9945873441 + 5775848001 = 99729^2 + 75999^2 .

It is a junction number, because it is equal to n+sod(n) for n = 15721721397 and 15721721406.

It is not an unprimeable number, because it can be changed into a prime (15721721443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 8911659 + ... + 8913422.

Almost surely, 2^15721721442 is an apocalyptic number.

15721721442 is an abundant number, since it is smaller than the sum of its proper divisors (23903435844).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

15721721442 is a wasteful number, since it uses less digits than its factorization.

15721721442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17825103 (or 17825093 counting only the distinct ones).

The product of its digits is 31360, while the sum is 36.

The spelling of 15721721442 in words is "fifteen billion, seven hundred twenty-one million, seven hundred twenty-one thousand, four hundred forty-two".