20721742 has 16 divisors (see below), whose sum is σ = 34644240. Its totient is φ = 9237888.

The previous prime is 20721737. The next prime is 20721749. The reversal of 20721742 is 24712702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721749) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15393 + ... + 16684.

It is an arithmetic number, because the mean of its divisors is an integer number (2165265).

Almost surely, 2^20721742 is an apocalyptic number.

20721742 is a deficient number, since it is larger than the sum of its proper divisors (13922498).

20721742 is a wasteful number, since it uses less digits than its factorization.

20721742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32115.

The product of its (nonzero) digits is 1568, while the sum is 25.

The square root of 20721742 is about 4552.1140143894. The cubic root of 20721742 is about 274.6684356591.

The spelling of 20721742 in words is "twenty million, seven hundred twenty-one thousand, seven hundred forty-two".