19721542 has 4 divisors (see below), whose sum is σ = 29582316. Its totient is φ = 9860770.

The previous prime is 19721539. The next prime is 19721543. The reversal of 19721542 is 24512791.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19721543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4930384 + ... + 4930387.

It is an arithmetic number, because the mean of its divisors is an integer number (7395579).

Almost surely, 2^19721542 is an apocalyptic number.

19721542 is a deficient number, since it is larger than the sum of its proper divisors (9860774).

19721542 is an equidigital number, since it uses as much as digits as its factorization.

19721542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9860773.

The product of its digits is 5040, while the sum is 31.

The square root of 19721542 is about 4440.8942793091. The cubic root of 19721542 is about 270.1761173777.

The spelling of 19721542 in words is "nineteen million, seven hundred twenty-one thousand, five hundred forty-two".